diff --git a/18/18.py b/18/18.py
new file mode 100644
index 0000000..ca91aae
--- /dev/null
+++ b/18/18.py
@@ -0,0 +1,245 @@
+from functools import reduce as freduce
+from itertools import permutations
+
+class Regular:
+    __slots__ = ['data']
+    def __init__(self, x):
+        self.data = x
+    def __str__(self):
+        return f'r{self.data}'
+    __repr__ = __str__
+    def __eq__(self, other):
+        if isinstance(other, Regular):
+            return self.data == other.data
+        if isinstance(other, int):
+            return self.data == other
+        return False
+
+def load_file(filename='input'):
+    with open(filename) as f:
+        for line in f:
+            yield line.strip()
+
+def add(x, y):
+    return reduce(add_numbers(x, y))
+
+def reduce(x):
+    while True:
+        if can_explode(x):
+            x = explode(x)
+            continue
+        if can_split(x):
+            x = split(x)
+            continue
+        break
+    return x
+
+def can_split(x):
+    try:
+        return next(filter(lambda k: k.data>=10, numbers(x)))
+    except StopIteration:
+        return False
+    
+def is_int(x):
+    return isinstance(x, int)
+
+def is_regular(x):
+    return isinstance(x, Regular)
+
+def is_pair(x):
+    return isinstance(x, list)
+
+def magnitude(x):
+    if is_regular(x):
+        return x.data
+    return 3*magnitude(first(x)) + 2*magnitude(second(x))
+
+def numbers(x):
+    if is_regular(x):
+        yield x
+    elif is_pair(x):
+        yield from numbers(first(x))
+        yield from numbers(second(x))
+
+def height(x, h=0):
+    if is_regular(first(x)) and is_regular(second(x)):
+        yield h, x
+    if is_pair(first(x)):
+        yield from height(first(x), h+1)
+    if is_pair(second(x)):
+        yield from height(second(x), h+1)
+
+def can_explode(x):
+    try:
+        return next(filter(lambda k: k[0]==4, height(x)))
+    except StopIteration:
+        return None
+
+def explode(where):
+    what = can_explode(where)[1]
+    replace_once(where, what, Regular(-1))
+    k = list(numbers(where))
+    i = k.index(Regular(-1))
+    if i-1>=0:
+        k[i-1].data += what[0].data
+    if i+1<len(k):
+        k[i+1].data += what[1].data
+    k[i].data = 0
+    update(where, iter(k))
+    return where
+
+def update(where, k):
+    if where == -1:
+        return
+    if is_regular(first(where)):
+        where[0] = next(k)
+    if is_pair(first(where)):
+        update(first(where), k)                   
+    if is_pair(second(where)):
+        update(second(where), k)
+    if is_regular(second(where)):
+        where[1] = next(k)
+
+
+def replace_once(where, what, with_):
+    def replace(where, what, with_):
+        nonlocal found
+        if is_pair(where):
+            if first(where) is what and not found:
+                where[0] = with_
+                found = True
+            elif second(where) is what and not found:
+                where[1] = with_
+                found = True
+            if not found and is_pair(first(where)):
+                replace(first(where), what, with_)
+            if not found and is_pair(second(where)):
+                replace(second(where), what, with_)
+    found = False
+    replace(where, what, with_)
+
+def split(where):
+    what = can_split(where)
+    with_ = [Regular(what.data//2), Regular((what.data+1)//2)]
+    replace_once(where, what, with_)
+    return where
+
+def first(x):
+    return x[0]
+
+def second(x):
+    return x[1]
+
+def add_numbers(x, y):
+    return [x,y]
+
+def from_string(s):
+    return regularize(eval(s))
+
+def regularize(x):
+    def rec(x):
+        if is_pair(x):
+            if is_int(first(x)):
+                x[0] = Regular(x[0])
+            else:
+                regularize(first(x))
+            if is_int(second(x)):
+                x[1] = Regular(x[1])
+            else:
+                regularize(second(x))
+    rec(x)
+    return x
+        
+
+def calculate(xs):
+    return freduce(add, map(from_string, xs))
+
+def test_magnitude():
+    assert magnitude(regularize([9,1]))==29
+    assert magnitude(regularize([1,9]))==21
+    assert 143==magnitude(regularize([[1,2],[[3,4],5]]))
+    assert 1384==magnitude(regularize([[[[0,7],4],[[7,8],[6,0]]],[8,1]]))
+    assert 445==magnitude(regularize([[[[1,1],[2,2]],[3,3]],[4,4]]))
+    assert 791==magnitude(regularize([[[[3,0],[5,3]],[4,4]],[5,5]]))
+    assert 1137==magnitude(regularize([[[[5,0],[7,4]],[5,5]],[6,6]]))
+    assert 3488==magnitude(regularize([[[[8,7],[7,7]],[[8,6],[7,7]]],[[[0,7],[6,6]],[8,7]]]))
+
+def test_can_explode():
+    assert can_explode(regularize([[[[[4,3],4],4],[7,[[8,4],9]]],[1,1]]))
+    assert can_explode(regularize([[[[0,7],4],[7,[[8,4],9]]],[1,1]]))
+    assert can_explode(regularize([[[[0,7],4],[[7,8],[0,[6,7]]]],[1,1]]))
+
+def test_can_split():
+    assert can_split(regularize([[[[0,7],4],[15,[0,13]]],[1,1]]))
+    assert can_split(regularize([[[[0,7],4],[[7,8],[0,13]]],[1,1]]))
+
+def test_split():
+    assert split(regularize([[[[0,7],4],[15,[0,13]]],[1,1]]))==[[[[0,7],4],[[7,8],[0,13]]],[1,1]]
+    assert split(regularize([[[[0,7],4],[[7,8],[0,13]]],[1,1]]))==[[[[0,7],4],[[7,8],[0,[6,7]]]],[1,1]]
+
+def test_explode():
+    assert explode(regularize([[[[[4,3],4],4],[7,[[8,4],9]]],[1,1]]))==[[[[0,7],4],[7,[[8,4],9]]],[1,1]]
+    assert explode(regularize([[[[0,7],4],[7,[[8,4],9]]],[1,1]]))==[[[[0,7],4],[15,[0,13]]],[1,1]]
+    assert explode(regularize([[[[0,7],4],[[7,8],[0,[6,7]]]],[1,1]]))==[[[[0,7],4],[[7,8],[6,0]]],[8,1]]
+    
+def test_add_simple():
+    t1 = """
+[1,1]
+[2,2]
+[3,3]
+[4,4]
+""".strip().split('\n')
+    assert calculate(t1)==[[[[1,1],[2,2]],[3,3]],[4,4]]  
+    t2 = """
+[1,1]
+[2,2]
+[3,3]
+[4,4]
+[5,5]
+""".strip().split('\n')
+    assert calculate(t2)==[[[[3,0],[5,3]],[4,4]],[5,5]]  
+    t3 = """
+[1,1]
+[2,2]
+[3,3]
+[4,4]
+[5,5]
+[6,6]
+""".strip().split('\n')
+    assert calculate(t3)==[[[[5,0],[7,4]],[5,5]],[6,6]]
+
+def test_add_example():
+    t = '''
+[[[[4,3],4],4],[7,[[8,4],9]]]
+[1,1]
+'''.strip().split('\n')
+    assert calculate(t)==[[[[0,7],4],[[7,8],[6,0]]],[8,1]]
+    
+def test_add_complex():
+    t4 = """
+[[[0,[4,5]],[0,0]],[[[4,5],[2,6]],[9,5]]]
+[7,[[[3,7],[4,3]],[[6,3],[8,8]]]]
+[[2,[[0,8],[3,4]]],[[[6,7],1],[7,[1,6]]]]
+[[[[2,4],7],[6,[0,5]]],[[[6,8],[2,8]],[[2,1],[4,5]]]]
+[7,[5,[[3,8],[1,4]]]]
+[[2,[2,2]],[8,[8,1]]]
+[2,9]
+[1,[[[9,3],9],[[9,0],[0,7]]]]
+[[[5,[7,4]],7],1]
+[[[[4,2],2],6],[8,7]]
+""".strip().split('\n')
+    assert calculate(t4[:2])==[[[[4,0],[5,4]],[[7,7],[6,0]]],[[8,[7,7]],[[7,9],[5,0]]]]
+    assert calculate(t4[:3])==[[[[6,7],[6,7]],[[7,7],[0,7]]],[[[8,7],[7,7]],[[8,8],[8,0]]]], 'похоже, при одинаковых заменах происходит пиздец'
+    assert calculate(t4[:4])==[[[[7,0],[7,7]],[[7,7],[7,8]]],[[[7,7],[8,8]],[[7,7],[8,7]]]]
+    assert calculate(t4[:5])==[[[[7,7],[7,8]],[[9,5],[8,7]]],[[[6,8],[0,8]],[[9,9],[9,0]]]]
+    assert calculate(t4[:6])==[[[[6,6],[6,6]],[[6,0],[6,7]]],[[[7,7],[8,9]],[8,[8,1]]]]
+    assert calculate(t4[:7])==[[[[6,6],[7,7]],[[0,7],[7,7]]],[[[5,5],[5,6]],9]]
+    assert calculate(t4[:8])==[[[[7,8],[6,7]],[[6,8],[0,8]]],[[[7,7],[5,0]],[[5,5],[5,6]]]]
+    assert calculate(t4[:9])==[[[[7,7],[7,7]],[[8,7],[8,7]]],[[[7,0],[7,7]],9]]
+    assert calculate(t4)==[[[[8,7],[7,7]],[[8,6],[7,7]]],[[[0,7],[6,6]],[8,7]]]  
+    
+    
+if __name__ == '__main__':
+    print(magnitude(calculate(load_file())))
+    print(max(magnitude(calculate(x)) for x in permutations(load_file(), 2)))
+    
diff --git a/18/input b/18/input
new file mode 100644
index 0000000..47e7ffb
--- /dev/null
+++ b/18/input
@@ -0,0 +1,100 @@
+[[[6,[0,5]],2],3]
+[[3,9],[[4,[5,5]],[9,4]]]
+[[3,[2,[0,7]]],[[1,[0,1]],[8,[2,4]]]]
+[[[[3,0],[8,1]],[[5,6],[3,5]]],[5,[[7,9],[5,1]]]]
+[[[9,5],1],[[2,6],[4,[4,6]]]]
+[2,[5,[3,0]]]
+[[[[3,8],9],[[9,2],[7,7]]],5]
+[[[[8,5],3],[0,[0,8]]],[9,[6,[8,1]]]]
+[[[[9,6],[9,1]],[[3,4],3]],[2,2]]
+[[3,[[7,7],2]],[[[9,9],[8,6]],2]]
+[[[[3,5],8],[4,[9,4]]],7]
+[[1,[6,[2,6]]],[[7,0],[[3,1],9]]]
+[[[[0,5],0],[0,[2,4]]],[7,[6,[1,6]]]]
+[0,[6,[3,1]]]
+[4,[[[1,2],0],[[6,3],6]]]
+[[[[4,3],[8,5]],[9,[0,5]]],[[[8,1],3],[8,8]]]
+[[3,[6,7]],[[[1,4],[2,1]],[9,[2,8]]]]
+[[[[3,0],[4,5]],4],[[3,[5,7]],6]]
+[[8,[5,[3,9]]],[[[1,9],[8,7]],7]]
+[[[0,[3,4]],[[0,1],6]],[1,5]]
+[6,[[9,4],[9,0]]]
+[[4,9],[[[0,9],9],8]]
+[5,[0,[3,6]]]
+[[[[3,9],[1,1]],[4,0]],[4,[[5,7],6]]]
+[[[6,[2,1]],[4,[3,3]]],[[6,[5,6]],[7,[5,0]]]]
+[[[8,4],[[1,2],[2,0]]],[[6,[5,6]],[6,4]]]
+[[[5,9],7],[[[3,4],[2,1]],2]]
+[[[8,8],5],[6,[[9,1],1]]]
+[[[[3,4],1],[1,[4,2]]],[[[9,1],[2,0]],3]]
+[[[5,[1,7]],[3,[9,7]]],[[2,0],[[7,7],5]]]
+[[[6,9],6],[6,[[4,2],[5,3]]]]
+[[[[6,5],[5,0]],[[6,9],7]],6]
+[[[[2,8],[3,2]],[8,8]],[[[4,6],7],[2,[2,3]]]]
+[[[3,4],1],5]
+[[6,[[7,4],8]],[[6,[9,2]],9]]
+[[[[0,4],0],[[3,1],[3,6]]],[0,[[2,8],[5,5]]]]
+[[5,[[1,2],6]],[[[1,9],[2,2]],[9,[1,0]]]]
+[[[[7,7],5],[[0,0],[0,5]]],[[5,4],[5,[8,1]]]]
+[[[[8,7],6],[0,[0,3]]],[2,[[9,8],0]]]
+[6,7]
+[[[[5,2],[2,2]],[[8,1],[2,7]]],2]
+[[[1,0],[[9,8],[2,1]]],4]
+[[[[5,2],[2,0]],7],[[2,[4,4]],[3,3]]]
+[[8,3],[[7,2],[[1,5],9]]]
+[[[[9,4],[7,5]],[[4,9],1]],[[[0,6],[1,6]],[[4,2],3]]]
+[4,[5,[5,3]]]
+[[1,[[0,1],6]],[[[8,8],6],0]]
+[[[0,3],[1,2]],[[6,8],[7,[4,7]]]]
+[3,[[[5,8],[6,9]],[8,[5,4]]]]
+[[1,1],[[8,[7,0]],9]]
+[2,2]
+[[3,[[0,4],1]],[[7,[2,3]],[8,4]]]
+[[[0,2],[5,[5,6]]],[[[8,1],[5,2]],8]]
+[[[[9,5],6],[[7,2],[2,1]]],[[[0,0],0],[[7,9],[9,1]]]]
+[[1,7],[1,[[6,3],8]]]
+[4,[[[7,4],1],[[1,9],6]]]
+[[[[7,8],9],3],[[[5,0],9],8]]
+[[[1,3],[[8,3],[1,9]]],[[[6,2],5],5]]
+[[8,[[6,6],[1,4]]],[[2,[9,0]],[9,[2,2]]]]
+[[0,[[1,6],8]],[[[3,7],[9,2]],[3,[3,6]]]]
+[[0,[5,6]],[[[6,5],1],8]]
+[[[[9,0],[1,1]],[[1,0],1]],[[[2,5],7],[5,[0,3]]]]
+[2,[2,[[3,8],[5,5]]]]
+[[[[4,0],2],[4,2]],[[5,[8,1]],[[2,7],6]]]
+[[[1,[3,5]],6],0]
+[[[3,3],[1,[2,1]]],[[3,[1,1]],[7,0]]]
+[[[[8,5],3],[2,[3,0]]],[[[4,8],[8,8]],[9,[2,0]]]]
+[[[[8,3],[9,8]],[[8,3],2]],[5,[5,8]]]
+[[[1,9],8],[[[0,3],[9,1]],[[9,1],[4,2]]]]
+[[[4,1],6],[[5,2],[4,2]]]
+[[7,[5,[3,0]]],[[0,[0,1]],[1,[9,6]]]]
+[[[[0,3],[8,9]],1],[6,2]]
+[[5,[7,8]],[[5,3],[[9,8],[6,2]]]]
+[[[[3,6],8],9],[[3,[6,2]],[0,1]]]
+[[[5,3],[6,[0,3]]],6]
+[[[2,9],7],[[[4,2],9],8]]
+[[[7,[3,5]],[6,[5,9]]],[[[3,2],[5,6]],1]]
+[[0,[[9,1],6]],8]
+[[[[3,5],[2,2]],[[9,8],9]],[8,8]]
+[[[[6,9],[2,0]],[6,1]],[1,5]]
+[[[0,[9,9]],[[3,1],9]],[[[4,8],2],[3,[4,8]]]]
+[[[5,3],[6,3]],[6,[[2,7],[3,2]]]]
+[[[5,[7,3]],8],[[2,[0,0]],[9,5]]]
+[[[7,[4,3]],[[9,6],[5,7]]],[[[1,8],[3,0]],[[2,4],[7,3]]]]
+[[[3,[2,1]],[1,2]],[7,[[5,4],8]]]
+[[4,[[2,6],[7,9]]],[[[1,8],3],[[0,1],[5,4]]]]
+[[[4,0],4],[3,7]]
+[[[4,[7,7]],5],[2,3]]
+[[[[7,7],[9,3]],8],[[[3,8],6],[[1,2],[9,6]]]]
+[[7,[[7,5],[7,8]]],[2,[[4,3],[6,3]]]]
+[[[7,3],[[8,2],[6,5]]],1]
+[[8,[7,[9,6]]],[5,[[2,2],2]]]
+[[[3,[8,9]],[[3,8],[3,3]]],[4,[7,[5,0]]]]
+[[[[2,0],[1,0]],3],[6,[[1,3],[5,4]]]]
+[[1,8],[8,[[6,7],3]]]
+[4,[[[3,4],[7,8]],[7,[7,1]]]]
+[[[4,8],[9,[7,4]]],6]
+[[[7,3],[[2,9],7]],[[[2,5],8],[2,5]]]
+[7,[[[8,7],0],[[3,1],6]]]
+[[6,[2,[3,2]]],[[[5,4],2],[[2,6],[8,4]]]]