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/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/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}"