diff --git a/.activate b/.activate
new file mode 100644
index 0000000..a3607ff
--- /dev/null
+++ b/.activate
@@ -0,0 +1,7 @@
+
+alias venv='source .venv/Scripts/activate'
+alias check='flake8 vpn_manager'
+alias format='black vpn_manager'
+alias test='pytest'
+
+venv
diff --git a/.gitignore b/.gitignore
index 09875ae..11ba77a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -162,4 +162,4 @@ cython_debug/
 #  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
 #  and can be added to the global gitignore or merged into this file.  For a more nuclear
 #  option (not recommended) you can uncomment the following to ignore the entire idea folder.
-#.idea/
+.idea/
diff --git a/README.md b/README.md
index c5f97b1..9e19b31 100644
--- a/README.md
+++ b/README.md
@@ -26,4 +26,4 @@ run
 # script declared in pyproject.toml
 $ example
 run
-```
\ No newline at end of file
+```
diff --git a/archive/_test_cidr4_merger.py b/archive/_test_cidr4_merger.py
new file mode 100644
index 0000000..c891934
--- /dev/null
+++ b/archive/_test_cidr4_merger.py
@@ -0,0 +1,395 @@
+import pytest
+
+from cidr4_merger import (
+    Cidr4MergerError,
+    cidr4_to_node,
+    find_neighbours_singles,
+    get_group_with_max_mask_len,
+    get_net_addr,
+    get_parent_ip,
+    have_same_parent,
+    lift_lonely_node,
+    make_cidr4,
+    make_groups,
+    make_parent,
+    merge_neighbors,
+    merge_nodes_cycle,
+    merge_nodes_deprecated,
+    merge_nodes_recursion,
+    reduce_nodes,
+    sort_nodes,
+)
+
+from .cidr4_data_for_tests import test_cidr4_data
+
+
+def test_true():
+    assert True
+
+
+bin_a = "10011000000000001000010000010000"
+assert len(bin_a) == 32
+ip_a = int(bin_a, 2)
+
+bin_b = "10011100000000000000000000101011"
+assert len(bin_b) == 32
+ip_b = int(bin_b, 2)
+
+bin_c = "10011000000000000000000000000000"
+assert len(bin_c) == 32
+ip_c = int(bin_c, 2)
+
+bin_d = "11111100000000000000000000000000"
+assert len(bin_c) == 32
+ip_d = int(bin_d, 2)
+
+
+def test_cidr4_to_node():
+    assert cidr4_to_node("4.78.139.0/24") == (72256256, 24, 0, 72256000)
+    assert cidr4_to_node("0.0.0.0/32") == (0, 32, 0, 0)
+
+    assert cidr4_to_node("23.234.30.0/24") == (401219072, 24, 0, 401219072)
+    assert cidr4_to_node("172.217.0.0/19") == (2899902464, 19, 0, 2899902464)
+    assert cidr4_to_node("23.225.141.0/24") == (400657664, 24, 0, 400657408)
+    assert cidr4_to_node("31.13.94.0/23") == (520969728, 23, 0, 520969216)
+
+    assert cidr4_to_node("0.0.0.0/2") == (0, 2, 0, 0)
+    assert cidr4_to_node("64.0.0.0/2") == (1073741824, 2, 0, 0)
+    assert cidr4_to_node("128.0.0.0/2") == (2147483648, 2, 0, 2147483648)
+    assert cidr4_to_node("192.0.0.0/2") == (3221225472, 2, 0, 2147483648)
+
+
+def test_make_cidr4():
+    assert make_cidr4(72256256, 24) == "4.78.139.0/24"
+    assert make_cidr4(0, 32) == "0.0.0.0/32"
+
+    assert make_cidr4(401219072, 24) == "23.234.30.0/24"
+    assert make_cidr4(2899902464, 19) == "172.217.0.0/19"
+    assert make_cidr4(400657664, 24) == "23.225.141.0/24"
+    assert make_cidr4(520969728, 23) == "31.13.94.0/23"
+
+
+def test_get_net_addr():
+    assert get_net_addr(ip_a, 5) == ip_c
+    assert get_net_addr(ip_b, 5) == ip_c
+    assert get_net_addr(0, 1) == 0
+    assert get_net_addr(0, 0) == 0
+
+
+def test_get_parent_mask():
+    assert get_parent_ip(ip_a, 6) == ip_c
+    assert get_parent_ip(ip_b, 6) == ip_c
+    assert get_parent_ip(0, 1) == 0
+
+    with pytest.raises(Exception) as exc_info:
+        get_parent_ip(0, 0)
+    assert str(exc_info.value) == "The top of the tree has no parent!"
+    assert exc_info.type is Cidr4MergerError
+
+
+def test_have_same_parent():
+    assert have_same_parent(ip_c, 6, ip_c, 6) is True
+    assert have_same_parent(ip_c, 6, ip_c, 5) is False
+    assert have_same_parent(ip_a, 6, ip_d, 6) is False
+    assert have_same_parent(ip_a, 6, 0, 1) is False
+    assert have_same_parent(ip_a, 6, 0, 0) is False
+
+
+def test_sort_nodes():
+    assert sort_nodes(
+        [
+            (401219072, 24, 0, 401219072),
+            (2899902464, 19, 0, 2899902464),
+            (400657664, 24, 0, 400657408),
+            (520969728, 23, 0, 520969216),
+        ]
+    ) == [
+        (2899902464, 19, 0, 2899902464),
+        (520969728, 23, 0, 520969216),
+        (400657664, 24, 0, 400657408),
+        (401219072, 24, 0, 401219072),
+    ]
+
+
+def test_get_group_with_max_mask_len():
+    assert get_group_with_max_mask_len(
+        [
+            (2899902464, 19, 0, 2899902464),
+            (520969728, 23, 0, 520969216),
+            (400657664, 24, 0, 400657408),
+            (401219072, 24, 0, 401219072),
+        ]
+    ) == [(400657664, 24, 0, 400657408), (401219072, 24, 0, 401219072)]
+
+    assert get_group_with_max_mask_len(
+        [
+            (401219072, 24, 0, 401219072),
+            (2899902464, 19, 0, 2899902464),
+            (520969728, 23, 0, 520969216),
+        ]
+    ) == [(401219072, 24, 0, 401219072)]
+
+
+def test_make_parent():
+    assert make_parent((0, 2, 12, 0), (1073741824, 2, 3, 0)) == (0, 1, 15, 0)
+    assert make_parent(
+        (2147483648, 2, 1, 2147483648), (3221225472, 2, 2, 2147483648)
+    ) == (2147483648, 1, 3, 0)
+
+    with pytest.raises(Exception) as exc_info:
+        make_parent((0, 2, 12, 0), (3221225472, 2, 2, 2147483648))
+    assert str(exc_info.value) == "Nodes must be neighbors!"
+    assert exc_info.type is Cidr4MergerError
+
+
+def test_reduce_nodes():
+    assert reduce_nodes(
+        [
+            (0, 2, 12, 0),
+            (1073741824, 2, 3, 0),
+        ]
+    ) == [
+        (0, 1, 15, 0),
+    ]
+
+    assert reduce_nodes(
+        [
+            (0, 2, 12, 0),
+            (1073741824, 2, 3, 0),
+            (2147483648, 2, 1, 2147483648),
+            (3221225472, 2, 2, 2147483648),
+        ]
+    ) == [
+        (2147483648, 1, 3, 0),
+        (0, 2, 12, 0),
+        (1073741824, 2, 3, 0),
+    ]
+
+    assert reduce_nodes(
+        [
+            (0, 2, 12, 0),
+            (2147483648, 1, 0, 0),
+        ]
+    ) == [
+        (0, 1, 12 + 2**30, 0),
+        (2147483648, 1, 0, 0),
+    ]
+
+    with pytest.raises(Exception) as exc_info:
+        reduce_nodes(
+            [
+                (0, 1, 12 + 2**30, 0),
+                (2147483648, 1, 0, 0),
+            ]
+        )
+    assert exc_info.type is Cidr4MergerError
+    assert str(exc_info.value) == "The top of the tree has no parent!"
+
+
+def test_merge_nodes_deprecated():
+    assert merge_nodes_deprecated(
+        [
+            (0, 2, 12, 0),
+            (2147483648, 2, 1, 2147483648),
+            (3221225472, 2, 2, 2147483648),
+        ],
+        2,
+    ) == [
+        (2147483648, 1, 3, 0),
+        (0, 2, 12, 0),
+    ]
+
+    with pytest.raises(Exception) as exc_info:
+        merge_nodes_deprecated(
+            [
+                (0, 2, 12, 0),
+                (2147483648, 2, 1, 2147483648),
+                (3221225472, 2, 2, 2147483648),
+            ],
+            1,
+        )
+    assert exc_info.type is Cidr4MergerError
+    assert str(exc_info.value) == "The top of the tree has no parent!"
+
+
+def test_make_groups():
+    nodes = [
+        (2398793728, 20, 0, 2398789632),
+        (2899943424, 20, 0, 2899943424),
+        (3627728896, 20, 0, 3627728896),
+        (520963072, 22, 0, 520962048),
+        (1089054720, 22, 0, 1089054720),
+        (2899902464, 19, 0, 2899902464),
+        (2915221504, 19, 0, 2915221504),
+    ]
+    assert dict(make_groups(nodes)) == {
+        20: [
+            (2398793728, 20, 0, 2398789632),
+            (2899943424, 20, 0, 2899943424),
+            (3627728896, 20, 0, 3627728896),
+        ],
+        22: [(520963072, 22, 0, 520962048), (1089054720, 22, 0, 1089054720)],
+        19: [(2899902464, 19, 0, 2899902464), (2915221504, 19, 0, 2915221504)],
+    }
+
+
+@pytest.fixture
+def nodes_only_neighbours():
+    return [
+        (0, 2, 12, 0),
+        (1073741824, 2, 3, 0),
+        (2147483648, 2, 1, 2147483648),
+        (3221225472, 2, 2, 2147483648),
+    ]
+
+
+@pytest.fixture
+def nodes_only_singles():
+    return [
+        (0, 2, 12, 0),
+        (2147483648, 2, 1, 2147483648),
+    ]
+
+
+@pytest.fixture
+def nodes_with_neighbours_n_singles():
+    return [
+        (0, 2, 12, 0),
+        (1073741824, 2, 3, 0),
+        (2147483648, 2, 1, 2147483648),
+    ]
+
+
+@pytest.fixture
+def groups_only_neighbours(nodes_only_neighbours):
+    return make_groups(nodes_only_neighbours)
+
+
+@pytest.fixture
+def groups_only_singles(nodes_only_singles):
+    return make_groups(nodes_only_singles)
+
+
+@pytest.fixture
+def groups_with_neighbours_n_singles(nodes_with_neighbours_n_singles):
+    return make_groups(nodes_with_neighbours_n_singles)
+
+
+def test_find_neighbours_singles(
+    groups_only_neighbours,
+    groups_only_singles,
+    groups_with_neighbours_n_singles,
+):
+    assert find_neighbours_singles(groups_only_neighbours) == (
+        [
+            ((0, 2, 12, 0), (1073741824, 2, 3, 0)),
+            ((2147483648, 2, 1, 2147483648), (3221225472, 2, 2, 2147483648)),
+        ],
+        [],
+    )
+
+    assert find_neighbours_singles(groups_only_singles) == (
+        [],
+        [(0, 2, 12, 0), (2147483648, 2, 1, 2147483648)],
+    )
+
+    assert find_neighbours_singles(groups_with_neighbours_n_singles) == (
+        [((0, 2, 12, 0), (1073741824, 2, 3, 0))],
+        [(2147483648, 2, 1, 2147483648)],
+    )
+
+
+def test_merge_neighbors__only_neighbours(nodes_only_neighbours):
+    new_nodes = merge_neighbors(
+        nodes_only_neighbours,
+        [
+            ((0, 2, 12, 0), (1073741824, 2, 3, 0)),
+            ((2147483648, 2, 1, 2147483648), (3221225472, 2, 2, 2147483648)),
+        ],
+    )
+    assert new_nodes == [
+        (0, 1, 15, 0),
+        (2147483648, 1, 3, 0),
+    ]
+
+
+def test_merge_neighbors__neighbours_n_singles(nodes_with_neighbours_n_singles):
+    new_nodes = merge_neighbors(
+        nodes_with_neighbours_n_singles,
+        [((0, 2, 12, 0), (1073741824, 2, 3, 0))],
+    )
+    assert new_nodes == [
+        (0, 1, 15, 0),
+        (2147483648, 2, 1, 2147483648),
+    ]
+
+
+def test_lift_lonely_node(nodes_only_singles):
+    singles = [(0, 2, 12, 0), (2147483648, 2, 1, 2147483648)]
+    new_nodes = lift_lonely_node(nodes_only_singles, singles)
+    assert new_nodes == [(2147483648, 1, 1073741825, 0), (0, 2, 12, 0)]
+
+
+def test_merge_nodes_recursion():
+    assert merge_nodes_recursion(
+        [
+            (0, 2, 12, 0),
+            (2147483648, 2, 1, 2147483648),
+            (3221225472, 2, 2, 2147483648),
+        ],
+        2,
+    ) == [
+        (2147483648, 1, 3, 0),
+        (0, 2, 12, 0),
+    ]
+
+    with pytest.raises(Exception) as exc_info:
+        merge_nodes_recursion(
+            [
+                (0, 2, 12, 0),
+                (2147483648, 2, 1, 2147483648),
+                (3221225472, 2, 2, 2147483648),
+            ],
+            1,
+        )
+    assert exc_info.type is Cidr4MergerError
+    assert str(exc_info.value) == "The top of the tree has no parent!"
+
+
+def test_merge_nodes_cycle():
+    assert merge_nodes_cycle(
+        [
+            (0, 2, 12, 0),
+            (2147483648, 2, 1, 2147483648),
+            (3221225472, 2, 2, 2147483648),
+        ],
+        2,
+    ) == [
+        (2147483648, 1, 3, 0),
+        (0, 2, 12, 0),
+    ]
+
+    with pytest.raises(Exception) as exc_info:
+        merge_nodes_cycle(
+            [
+                (0, 2, 12, 0),
+                (2147483648, 2, 1, 2147483648),
+                (3221225472, 2, 2, 2147483648),
+            ],
+            1,
+        )
+    assert exc_info.type is Cidr4MergerError
+    assert str(exc_info.value) == "The top of the tree has no parent!"
+
+
+def test_merge_nodes_recursion_vs_cycle():
+    required_len = 20
+
+    test_data = test_cidr4_data.strip().splitlines()
+    test_nodes = list(map(cidr4_to_node, test_data))
+    test_nodes = sort_nodes(test_nodes)
+
+    merged_nodes_recursion = merge_nodes_recursion(test_nodes, required_len)
+    merged_nodes_cycle = merge_nodes_cycle(test_nodes, required_len)
+
+    assert merged_nodes_recursion == merged_nodes_cycle
diff --git a/archive/cidr4_merger.py b/archive/cidr4_merger.py
new file mode 100644
index 0000000..7dfa3d0
--- /dev/null
+++ b/archive/cidr4_merger.py
@@ -0,0 +1,226 @@
+import cProfile
+import sys
+from collections import defaultdict
+
+sys.setrecursionlimit(10_000)
+
+Node = tuple[int, int, int, int]
+
+
+class Cidr4MergerError(Exception):
+    pass
+
+
+def get_data(input_file):
+    with open(input_file, "r") as file:
+        data = file.read().splitlines()
+    return data
+
+
+def cidr4_to_node(cidr4: str) -> Node:
+    ip_address, mask_len = cidr4.strip().split("/")
+    mask_len = int(mask_len)
+    a, b, c, d = list(map(int, ip_address.split(".")))
+    ip = a * 256**3 + b * 256**2 + c * 256**1 + d * 256**0
+    added_ips_number = 0
+    parent_ip = get_parent_ip(ip, mask_len)
+    return ip, mask_len, added_ips_number, parent_ip
+
+
+def sort_nodes(nodes: list[Node]) -> list[Node]:
+    return sorted(nodes, key=lambda x: (x[1], x[0]))
+
+
+def get_net_addr(ip: int, mask_len: int) -> int:
+    mask = ((1 << mask_len) - 1) << (32 - mask_len)
+    net_addr = ip & mask
+    return net_addr
+
+
+def get_parent_ip(ip: int, mask_len: int) -> int:
+    if mask_len == 0:
+        raise Cidr4MergerError("The top of the tree has no parent!")
+    return get_net_addr(ip, mask_len - 1)
+
+
+def have_same_parent(mask_len_a, parent_ip_a, mask_len_b, parent_ip_b) -> bool:
+    return mask_len_a == mask_len_b and parent_ip_a == parent_ip_b
+
+
+def get_group_with_max_mask_len(nodes: list[Node]) -> list[Node]:
+    max_mask_len = max(nodes, key=lambda x: x[1])[1]
+    return list(filter(lambda x: x[1] == max_mask_len, nodes))
+
+
+def make_parent(a: Node, b: Node | None = None) -> Node:
+    ip_a, mask_len_a, added_ips_number_a, parent_ip_a = a
+    if b:
+        ip_b, mask_len_b, added_ips_b, parent_ip_b = b
+        if not have_same_parent(mask_len_a, parent_ip_a, mask_len_b, parent_ip_b):
+            raise Cidr4MergerError("Nodes must be neighbors!")
+        added_ips_number = added_ips_number_a + added_ips_b
+    else:
+        added_ips_number = added_ips_number_a + 2 ** (32 - mask_len_a)
+    ip = parent_ip_a
+    mask_len = mask_len_a - 1
+    parent_ip = get_parent_ip(ip, mask_len)
+    return ip, mask_len, added_ips_number, parent_ip
+
+
+def reduce_nodes(nodes: list[Node]) -> list[Node]:
+    group = get_group_with_max_mask_len(nodes)
+
+    neighbours = []
+    loners = []
+    i = 0
+    while i < len(group) - 1:
+        a, b = group[i], group[i + 1]
+        ip_a, mask_len_a, _, parent_ip_a = a
+        ip_b, mask_len_b, _, parent_ip_b = b
+        if have_same_parent(mask_len_a, parent_ip_a, mask_len_b, parent_ip_b):
+            neighbours.append((a, b))
+            i += 2
+        else:
+            loners.append(a)
+            i += 1
+    if i == len(group) - 1:
+        loners.append(group[i])
+
+    if neighbours:
+        zipped = zip(neighbours, map(lambda x: make_parent(x[0], x[1]), neighbours))
+        min_zipped = min(zipped, key=lambda x: x[1][2])
+        (a, b), parent = min_zipped
+        nodes.remove(a)
+        nodes.remove(b)
+        nodes.append(parent)
+    elif loners:
+        zipped = zip(loners, map(make_parent, loners))
+        min_zipped = min(zipped, key=lambda x: x[1][2])
+        a, parent = min_zipped
+        nodes.remove(a)
+        nodes.append(parent)
+    else:
+        assert False, "Error"
+
+    return sort_nodes(nodes)
+
+
+def merge_nodes_deprecated(nodes: list[Node], required_len: int) -> list[Node]:
+    while len(nodes) > required_len:
+        nodes = reduce_nodes(nodes)
+    return nodes
+
+
+def make_cidr4(ip, mask_len) -> str:
+    lst = [str(ip >> (i << 3) & 0xFF) for i in reversed(range(4))]
+    ip_address = ".".join(lst)
+    return f"{ip_address}/{mask_len}"
+
+
+def lift_lonely_node(nodes: list[Node], singles: list[Node]) -> list[Node]:
+    # find single whose parent has the least added addresses
+    min_single, min_parent = singles[0], make_parent(singles[0])
+    for node in singles[1:]:
+        parent = make_parent(node)
+        if parent[2] < min_parent[2]:
+            min_single, min_parent = node, parent
+
+    nodes.remove(min_single)
+    nodes.append(min_parent)
+    nodes = sort_nodes(nodes)
+    return nodes
+
+
+def merge_neighbors(
+    nodes: list[Node], neighbours: list[tuple[Node, Node]]
+) -> list[Node]:
+    for a, b in neighbours:
+        parent = make_parent(a, b)
+        nodes.remove(a)
+        nodes.remove(b)
+        nodes.append(parent)
+    return sort_nodes(nodes)
+
+
+def find_neighbours_singles(groups: defaultdict) -> tuple[list, list]:
+    neighbours = []
+    singles = []
+    for group in groups.values():
+        i = 0
+        while i < len(group) - 1:
+            a, b = group[i], group[i + 1]
+            ip_a, mask_len_a, _, parent_ip_a = a
+            ip_b, mask_len_b, _, parent_ip_b = b
+            if have_same_parent(mask_len_a, parent_ip_a, mask_len_b, parent_ip_b):
+                neighbours.append((a, b))
+                i += 2
+            else:
+                singles.append(a)
+                i += 1
+        if i == len(group) - 1:
+            singles.append(group[i])
+    return neighbours, singles
+
+
+def make_groups(nodes: list[Node]) -> defaultdict:
+    groups = defaultdict(list)
+    for n in nodes:
+        groups[n[1]].append(n)
+    return groups
+
+
+def merge_nodes_recursion(nodes: list[Node], required_len: int) -> list[Node]:
+    if len(nodes) <= required_len:
+        return nodes
+    groups = make_groups(nodes)
+    neighbours, singles = find_neighbours_singles(groups)
+    if neighbours:
+        new_nodes = merge_neighbors(nodes, neighbours)
+        return merge_nodes_recursion(new_nodes, required_len)
+    new_nodes = lift_lonely_node(nodes, singles)
+    return merge_nodes_recursion(new_nodes, required_len)
+
+
+def merge_nodes_cycle(nodes_to_merge: list[Node], required_len: int) -> list[Node]:
+    nodes = [x for x in nodes_to_merge]
+    while not len(nodes) <= required_len:
+        groups = make_groups(nodes)
+        neighbours, singles = find_neighbours_singles(groups)
+        if neighbours:
+            nodes = merge_neighbors(nodes, neighbours)
+        elif singles:
+            nodes = lift_lonely_node(nodes, singles)
+        else:
+            raise Cidr4MergerError("Invalid case!")
+    return nodes
+
+
+def main():
+    file = "cidr4.txt"
+    required_len = 20
+
+    data = get_data(file)
+    nodes = list(map(cidr4_to_node, data))
+
+    nodes = sort_nodes(nodes)
+    # merged_nodes = merge_nodes_deprecated(nodes, required_len)
+    # merged_nodes = merge_nodes_recursion(nodes, required_len)
+    merged_nodes = merge_nodes_cycle(nodes, required_len)
+
+    cidr4s = []
+    sum_added_ips = 0
+    for ip_value, mask_len, added_ips, _ in merged_nodes:
+        cidr4s.append(make_cidr4(ip_value, mask_len))
+        sum_added_ips += added_ips
+
+    cidr4s_str = "\n".join(cidr4s)
+    print(
+        f"Исходный список длины {len(nodes)} сокращен до {len(cidr4s)}\n"
+        f"Количество добавленных ip адресов: {sum_added_ips:_}\n"
+        f"Список объединенных cidr4:\n"
+        f"{cidr4s_str}"
+    )
+
+
+if __name__ == "__main__":
+    cProfile.run("main()")
diff --git a/archive/insurance_functions_example.md b/archive/insurance_functions_example.md
new file mode 100644
index 0000000..8b1a256
--- /dev/null
+++ b/archive/insurance_functions_example.md
@@ -0,0 +1,30 @@
+```python
+def find_subnets(nodes: list[Node]) -> list[tuple[Node, Node]]:
+    subnets = []
+    for i, (a, b) in enumerate(zip(nodes, nodes[1:])):
+        parent_node, dip = merge_two_nodes(a, b)
+        if parent_node == a or parent_node == b:
+            subnets.append((a, b))
+    return subnets
+
+
+def ensure_no_subnets(nodes: list[Node]):
+    if subnets := find_subnets(nodes):
+        raise Cidr4MergerError(f"There are subnets! {subnets=}")
+```
+
+
+```python
+def find_neighbors(nodes: list[Node]) -> list[tuple[Node, Node]]:
+    neighbors = []
+    for i, (a, b) in enumerate(zip(nodes, nodes[1:])):
+        parent_node, dip = merge_two_nodes(a, b)
+        if parent_node[1] + 1 == a[1] == b[1]:
+            neighbors.append((a, b))
+    return neighbors
+
+
+def ensure_no_neighbors(nodes: list[Node]):
+    if neighbors := find_neighbors(nodes):
+        raise Cidr4MergerError(f"There are neighbors! {neighbors=}")
+```
diff --git a/cidr4.txt b/cidr4.txt
new file mode 100644
index 0000000..b3f117f
--- /dev/null
+++ b/cidr4.txt
@@ -0,0 +1,486 @@
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diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/cidr4_merge/test_cidr4_merger.py b/tests/cidr4_merge/test_cidr4_merger.py
new file mode 100644
index 0000000..6d636db
--- /dev/null
+++ b/tests/cidr4_merge/test_cidr4_merger.py
@@ -0,0 +1,70 @@
+from vpn_manager.cidr4_merge.cidr4_merger import find_neighbors, merge_nodes, solution
+
+
+def test_true():
+    assert True
+
+
+def test_merge_nodes():
+    assert merge_nodes((0, 32), (1, 32)) == ((0, 31), 0)
+    assert merge_nodes((0, 32), (2, 32)) == ((0, 30), 2)
+    assert merge_nodes((0, 32), (5, 32)) == ((0, 29), 6)
+    assert merge_nodes((3, 32), (4, 32)) == ((0, 29), 6)
+    assert merge_nodes((0, 32), (4, 30)) == ((0, 29), 3)
+    assert merge_nodes((0, 32), (6, 31)) == ((0, 29), 5)
+
+
+def test_find_neighbors():
+    assert find_neighbors([(0, 32), (2, 32), (4, 32), (6, 32)]) == []
+    assert find_neighbors([(0, 32), (1, 32)]) == [(0, (0, 32), (1, 32))]
+    assert find_neighbors(
+        [
+            (0, 32),
+            (1, 32),
+            (6, 32),
+            (7, 32),
+        ]
+    ) == [
+        (0, (0, 32), (1, 32)),
+        (2, (6, 32), (7, 32)),
+    ]
+    assert find_neighbors(
+        [
+            (0, 32),
+            (1, 32),
+            (6, 32),
+        ]
+    ) == [
+        (0, (0, 32), (1, 32)),
+    ]
+
+
+def test_solution():
+    assert solution(
+        [
+            (0, 32),
+            (3, 32),
+            (4, 32),
+        ],
+        2,
+    ) == ([(0, 30), (4, 32)], 2)
+
+    assert solution(
+        [
+            (0, 32),
+            (3, 32),
+            (4, 32),
+            (7, 32),
+        ],
+        2,
+    ) == ([(0, 29)], 4)
+
+    assert solution(
+        [
+            (0, 32),
+            (3, 32),
+            (4, 32),
+            (7, 32),
+        ],
+        1,
+    ) == ([(0, 29)], 4)
diff --git a/tests/cidr4_merge/test_solutions.py b/tests/cidr4_merge/test_solutions.py
new file mode 100644
index 0000000..091fb9b
--- /dev/null
+++ b/tests/cidr4_merge/test_solutions.py
@@ -0,0 +1,56 @@
+from vpn_manager.cidr4_merge.fast import solution as fast
+from vpn_manager.cidr4_merge.precise import solution as precise, f
+from vpn_manager.cidr4_merge.util import *
+
+
+def test_true():
+    assert True
+
+#cidrs = list(map(cidr4_to_node, get_data()))
+
+def test_fast_single_lifting():
+    assert ([(0, 30)], 0) ==\
+        fast([(0, 31), (2, 31)], 1)
+    assert ([(0, 29)], 2) ==\
+        fast([(0, 30), (4, 31)], 1)
+    assert ([(0, 29)], 3) ==\
+        fast([(0, 30), (4, 32)], 1)
+    
+def test_fast_double_lifting():
+    assert ([(0, 29)], 4) ==\
+        fast([(0, 31), (4, 31)], 1)
+        
+        
+def test_fast_subnets():
+    assert ([(0, 30)], 0) ==\
+        fast([(0, 30), (0, 31)], 1)
+    assert ([(0, 29)], 0) ==\
+        fast([(0, 29), (4, 31)], 1)
+
+
+def test_precise_single_lifting():
+    assert ([(0, 30)], 0) ==\
+        precise([(0, 31), (2, 31)], 1)
+    assert ([(0, 29)], 2) ==\
+        precise([(0, 30), (4, 31)], 1)
+    assert ([(0, 29)], 3) ==\
+        precise([(0, 30), (4, 32)], 1)
+    
+def test_precise_double_lifting():
+    assert ([(0, 29)], 4) ==\
+        precise([(0, 31), (4, 31)], 1)
+        
+        
+def test_precise_subnets():
+    assert ([(0, 30)], 0) ==\
+        precise([(0, 30), (0, 31)], 1)
+    assert ([(0, 29)], 0) ==\
+        precise([(0, 29), (4, 31)], 1)
+        
+def test_precise_f_single_lifting():
+    assert (0, (0, 30, 0)) ==\
+        f((0, 31, 0), (2, 31, 0))
+    assert (2, (0, 29, 2)) ==\
+        f((0, 30, 0), (4, 31, 0))
+    assert (3, (0, 29, 3)) ==\
+        f((0, 30, 0), (4, 32, 0))
diff --git a/tests/cidr4_merge/test_util.py b/tests/cidr4_merge/test_util.py
new file mode 100644
index 0000000..ea5eeb2
--- /dev/null
+++ b/tests/cidr4_merge/test_util.py
@@ -0,0 +1,30 @@
+from vpn_manager.cidr4_merge.util import cidr4_to_node, make_cidr4
+
+
+def test_true():
+    assert True
+
+
+def test_cidr4_to_node():
+    assert cidr4_to_node("4.78.139.0/24") == (72256256, 24)
+    assert cidr4_to_node("0.0.0.0/32") == (0, 32)
+
+    assert cidr4_to_node("23.234.30.0/24") == (401219072, 24)
+    assert cidr4_to_node("172.217.0.0/19") == (2899902464, 19)
+    assert cidr4_to_node("23.225.141.0/24") == (400657664, 24)
+    assert cidr4_to_node("31.13.94.0/23") == (520969728, 23)
+
+    assert cidr4_to_node("0.0.0.0/2") == (0, 2)
+    assert cidr4_to_node("64.0.0.0/2") == (1073741824, 2)
+    assert cidr4_to_node("128.0.0.0/2") == (2147483648, 2)
+    assert cidr4_to_node("192.0.0.0/2") == (3221225472, 2)
+
+
+def test_make_cidr4():
+    assert make_cidr4(72256256, 24) == "4.78.139.0/24"
+    assert make_cidr4(0, 32) == "0.0.0.0/32"
+
+    assert make_cidr4(401219072, 24) == "23.234.30.0/24"
+    assert make_cidr4(2899902464, 19) == "172.217.0.0/19"
+    assert make_cidr4(400657664, 24) == "23.225.141.0/24"
+    assert make_cidr4(520969728, 23) == "31.13.94.0/23"
diff --git a/vpn_manager/cidr4_merge/README.md b/vpn_manager/cidr4_merge/README.md
new file mode 100644
index 0000000..b3c65b0
--- /dev/null
+++ b/vpn_manager/cidr4_merge/README.md
@@ -0,0 +1,6 @@
+Run merging algorithms:
+```
+python -m vpn_manager.cidr4_merge.cidr4_merger
+python -m vpn_manager.cidr4_merge.fast
+python -m vpn_manager.cidr4_merge.precise
+```
diff --git a/vpn_manager/cidr4_merge/__init__.py b/vpn_manager/cidr4_merge/__init__.py
new file mode 100644
index 0000000..f8176bd
--- /dev/null
+++ b/vpn_manager/cidr4_merge/__init__.py
@@ -0,0 +1,2 @@
+class Cidr4MergerError(Exception):
+    pass
diff --git a/vpn_manager/cidr4_merge/cidr4_merger.py b/vpn_manager/cidr4_merge/cidr4_merger.py
new file mode 100644
index 0000000..683f1f7
--- /dev/null
+++ b/vpn_manager/cidr4_merge/cidr4_merger.py
@@ -0,0 +1,104 @@
+import cProfile
+
+from vpn_manager.cidr4_merge import Cidr4MergerError
+
+from .util import cidr4_to_node, get_data, make_cidr4
+
+Node = tuple[int, int]
+
+
+class EnsureNoSubnetError(Cidr4MergerError):
+    pass
+
+
+class EnsureNoNeighborsError(Cidr4MergerError):
+    pass
+
+
+def find_subnets(nodes: list[Node]) -> list[tuple[Node, Node]]:
+    subnets = []
+    for i, (a, b) in enumerate(zip(nodes, nodes[1:])):
+        parent_node, dip = merge_nodes(a, b)
+        if parent_node == a or parent_node == b:
+            subnets.append((a, b))
+    return subnets
+
+
+def ensure_no_subnets(nodes: list[Node]):
+    if subnets := find_subnets(nodes):
+        raise EnsureNoSubnetError(f"There are subnets! {subnets=}")
+
+
+def find_neighbors(nodes: list[Node]) -> list[tuple[int, Node, Node]]:
+    neighbors = []
+    for i, (a, b) in enumerate(zip(nodes, nodes[1:])):
+        parent_node, dip = merge_nodes(a, b)
+        if parent_node[1] + 1 == a[1] == b[1]:
+            neighbors.append((i, a, b))
+    return neighbors
+
+
+def ensure_no_neighbors(nodes: list[Node]):
+    if neighbors := find_neighbors(nodes):
+        raise EnsureNoNeighborsError(f"There are neighbors! {neighbors=}")
+
+
+def merge_nodes(a: Node, b: Node) -> tuple[Node, int]:
+    def find_parent(a, b):
+        ia, la = a
+        ib, lb = b
+        min_l = min(la, lb)
+        mask = ((1 << min_l) - 1) << (32 - min_l)
+        while ia & mask != ib & mask:
+            min_l -= 1
+            mask = (mask << 1) & ((1 << 32) - 1)
+        return ia & mask, min_l
+
+    def calc_dip(l1, lp):
+        m = lp + 1
+        res = 1 << (l1 - m)
+        res -= 1
+        res <<= 32 - l1
+        return res
+
+    p = find_parent(a, b)
+    dip = calc_dip(a[1], p[1]) + calc_dip(b[1], p[1])
+    return p, dip
+
+
+def solution(nodes: list[Node], req_len: int) -> tuple[list[Node], int]:
+    sum_dip = 0
+    while len(nodes) > req_len:
+        min_t = None, None, float("inf")
+        for i, (a, b) in enumerate(zip(nodes, nodes[1:])):
+            p, dip = merge_nodes(a, b)
+            if dip < min_t[2]:
+                min_t = i, p, dip
+            if dip == 0:
+                break
+        i, p, dip = min_t
+        nodes = nodes[:i] + [p] + nodes[i + 2 :]
+        sum_dip += dip
+
+    while nbs := find_neighbors(nodes):
+        i, a, b = nbs[0]
+        p, dip = merge_nodes(a, b)
+        nodes = nodes[:i] + [p] + nodes[i + 2 :]
+        sum_dip += dip
+
+    return nodes, sum_dip
+
+
+def main():
+    required_len = 20
+    data = get_data()
+    nodes = sorted(map(cidr4_to_node, data))
+    ensure_no_subnets(nodes)
+    ensure_no_neighbors(nodes)
+    merged_nodes, sum_dip = solution(nodes, required_len)
+    cidr4s = [make_cidr4(ip, mask_len) for ip, mask_len in merged_nodes]
+    print(cidr4s, sum_dip, sep="\n")
+
+
+if __name__ == "__main__":
+    cProfile.run("main()")
diff --git a/vpn_manager/cidr4_merge/fast.py b/vpn_manager/cidr4_merge/fast.py
new file mode 100644
index 0000000..ca65b46
--- /dev/null
+++ b/vpn_manager/cidr4_merge/fast.py
@@ -0,0 +1,43 @@
+from heapq import heapify, heappush, heappop
+from .util import mask, get_data, cidr4_to_node, make_cidr4
+
+
+def solution(cidrs, M):
+    h = []
+    d = {}
+    for ip, l in cidrs:
+        h.append((32-l, ip, l))
+        d[(ip, l)] = 0
+    heapify(h)
+    while len(h)>M:
+        x1, ip1, l1 = heappop(h)
+        x2, ip2, l2 = h[0]
+        if l1==l2 and ip1 & mask[l1-1] == ip2 & mask[l2-1]:
+            heappop(h)
+            if (ip1 & mask[l1-1], l1-1) not in d:
+                heappush(h, (x1+1, ip1 & mask[l1-1], l1-1))
+                d[(ip1 & mask[l1-1], l1-1)] = d[(ip1, l1)] + d[(ip2, l2)]
+            del d[(ip2, l2)]
+        else:
+            if (ip1 & mask[l1-1], l1-1) not in d:
+                heappush(h, (x1+1, ip1 & mask[l1-1], l1-1))
+                d[(ip1 & mask[l1-1], l1-1)] = d[(ip1, l1)] + 2**x1
+        del d[(ip1, l1)]
+        s = sum(d.values())
+        cidrs = list(d.keys())
+    return cidrs, s
+
+
+def main():
+    M = 20
+    a = get_data()
+    b = list(map(cidr4_to_node, a))
+    cidrs, s = solution(b, M)
+    cidrs = sorted([make_cidr4(*x) for x in cidrs])
+    print(cidrs, s, sep='\n')
+    
+
+if __name__=='__main__':
+    import cProfile
+    main()
+            
diff --git a/vpn_manager/cidr4_merge/precise.py b/vpn_manager/cidr4_merge/precise.py
new file mode 100644
index 0000000..8dcae41
--- /dev/null
+++ b/vpn_manager/cidr4_merge/precise.py
@@ -0,0 +1,59 @@
+from .util import mask, get_data, cidr4_to_node, make_cidr4
+
+
+def f(x, y):
+    t = x
+    b = y
+    if x[1]>y[1]:
+        t = y
+        b = x
+    ip1, l1, a1 = t
+    ip2, l2, a2 = b
+    if ip1 & mask[l1] == ip2 & mask[l1]:
+        return (0, t)
+    t1 = t2 = 0
+    while not l1==l2:
+        t2 += 2**(32-l2)
+        l2 -= 1
+        ip2 = ip2 & mask[l2]
+    while not ip1 & mask[l1-1] == ip2 & mask[l2-1]:
+        t1 += 2**(32-l1)
+        l1 -= 1
+        ip1 = ip1 & mask[l1]
+        t2 += 2**(32-l2)
+        l2 -= 1
+        ip2 = ip2 & mask[l2]
+    r = (ip1 & mask[l1-1], l1-1, a1+a2+t1+t2)
+    return (t1+t2, r)
+    
+
+def solution(cidrs, M):
+    cidrs = sorted((ip, l, 0) for ip, l in cidrs)
+    while len(cidrs)>M:
+        t = (None, float('+inf'), None)
+        for i, (x, y) in enumerate(zip(cidrs, cidrs[1:])):
+            m, r = f(x, y)
+            if m<t[1]:
+                t = (i, m, r)
+            if m==0:
+                break
+        cidrs[t[0]] = t[2]
+        del cidrs[t[0]+1]
+    s = sum(x[2] for x in cidrs)
+    cidrs = [x[:2] for x in cidrs]
+    return cidrs, s
+
+
+def main():
+    M = 20
+    a = get_data()
+    b = list(map(cidr4_to_node, a))
+    cidrs, s = solution(b, M)
+    cidrs = sorted([make_cidr4(*x) for x in cidrs])
+    print(cidrs, s, sep='\n')
+    
+    
+
+if __name__=='__main__':
+    import cProfile
+    main()
diff --git a/vpn_manager/cidr4_merge/util.py b/vpn_manager/cidr4_merge/util.py
new file mode 100644
index 0000000..f514611
--- /dev/null
+++ b/vpn_manager/cidr4_merge/util.py
@@ -0,0 +1,20 @@
+mask = [((1 << i) - 1) << (32 - i) for i in range(33)]
+
+
+def get_data(input_file='cidr4.txt'):
+    with open(input_file, "r") as file:
+        return file.read().splitlines()
+
+
+def cidr4_to_node(cidr4: str):
+    ip_address, mask_len = cidr4.strip().split("/")
+    mask_len = int(mask_len)
+    a, b, c, d = list(map(int, ip_address.split(".")))
+    ip = a * 256**3 + b * 256**2 + c * 256**1 + d * 256**0
+    return ip, mask_len
+
+
+def make_cidr4(ip, mask_len) -> str:
+    lst = [str(ip >> (i << 3) & 0xFF) for i in reversed(range(4))]
+    ip_address = ".".join(lst)
+    return f"{ip_address}/{mask_len}"