Strings A and B are K-similar (for some non-negative integer K) if we can swap the positions of two letters in A exactly K times so that the resulting string equals B.
Given two anagrams A and B, return the smallest K for which A and B are K-similar.
Example 1:
Input: A = "ab", B = "ba"
Output: 1


Example 2:
Input: A = "abc", B = "bca"
Output: 2


Example 3:
Input: A = "abac", B = "baca"
Output: 2


Example 4:
Input: A = "aabc", B = "abca"
Output: 2



Note:

1 <= A.length == B.length <= 20
A and B contain only lowercase letters from the set {'a', 'b', 'c', 'd', 'e', 'f'}

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

def _disabled_input(*args, **kwargs):
    raise RuntimeError("input() is disabled in callable mode")
builtins.input = _disabled_input

ns = {"__name__": "__judge__"}  # prevent if __name__ == "__main__" blocks
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'class Solution:\n    def kSimilarity(self, A: str, B: str) -> int:\n        A = list(A)\n        B = list(B)\n        \n        n = len(A)\n        \n        \n        # ans = 0\n        # for i in range(n):\n        #     if A[i]==B[i]:\n        #         continue\n        #     else:\n        #         ans+=1\n        #         for j in range(i+1, n):\n        #             if B[j] == A[i]:\n        #                 B[i], B[j] = B[j], B[i]\n        #                 break\n        # return ans\n        \n        def rec(i):\n            if i==n:\n                return 0\n            \n            if A[i]==B[i]:\n                return rec(i+1)\n            else:\n                min_ = sys.maxsize\n                for j in range(i+1, n):\n                    if B[j] == A[i] and B[j]!=A[j]:\n                        B[i], B[j] = B[j], B[i]\n                        min_ = min(min_, rec(i+1) + 1)\n                        B[i], B[j] = B[j], B[i]\n                return min_\n        \n        return rec(0)\n                        \n\n#         ans = 0\n#         for i in range(n):\n#             if A[i]==B[i]:\n#                 continue\n#             else:\n#                 ans+=1\n#                 for j in range(i+1, n):\n#                     if B[j] == A[i] and B[j]!=A[j]:\n#                         B[i], B[j] = B[j], B[i]\n#                         break\n#         return ans\n                        \n\n        \n#         def rec(i):\n#             if i==n:\n#                 return 0\n            \n#             if A[i]==B[i]:\n#                 return rec(i+1)\n#             else:\n#                 min_ = sys.maxsize\n#                 j = 0\n#                 while A[j]==B[j]:\n#                     j+=1\n#                 for k in range(j+1, n):\n#                     if B[k] == A[j]:\n#                         B[j], B[k] = B[k], B[j]\n#                         min_ = min(min_, rec(i+1) + 1)\n#                         B[j], B[k] = B[k], B[j]\n#                 return min_\n        \n#         return rec(0)\n#         def nei(x):\n#             i = 0\n#             while x[i] == B[i]: i+=1\n#             for j in range(i+1, len(x)):\n#                 if x[j] == B[i]: yield x[:i]+x[j]+x[i+1:j]+x[i]+x[j+1:]\n#         q, seen = [(A,0)], set([A])\n        \n#         for x, d in q:\n#             if x == B: return d\n#             for y in nei(x):\n#                 if y not in seen:\n#                     seen.add(y), q.append((y,d+1))\n'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'kSimilarity'
if _fn_name:
    if "Solution" in ns:
        try:
            _obj = ns["Solution"]()
            if hasattr(_obj, _fn_name):
                _target = getattr(_obj, _fn_name)
        except Exception:
            _target = None
    if _target is None and _fn_name in ns and callable(ns[_fn_name]):
        _target = ns[_fn_name]
# Fallback: if there's exactly one user-defined function, use it
if _target is None:
    _cands = [v for k, v in ns.items() if callable(v) and getattr(v, "__module__", "") in ("__judge__", "__main__")]
    _user_funcs = [c for c in _cands if getattr(c, "__name__", "").startswith("_") is False]
    if len(_user_funcs) == 1:
        _target = _user_funcs[0]
if _target is None:
    raise RuntimeError(f"Could not resolve callable '{_fn_name}'")

_raw = sys.stdin.read().strip()
if _raw:
    _parsed = json.loads(_raw)
    if isinstance(_parsed, dict):
        _kwargs = _parsed.get("kwargs", {})
        _args = _parsed.get("args", [])
    else:
        _args, _kwargs = _parsed, {}
else:
    _args, _kwargs = [], {}
if not isinstance(_args, (list, tuple)):
    _args = [_args]
_res = _target(*_args, **_kwargs)
try:
    sys.stdout.write(repr(_res) + "\n")
except Exception:
    pass

```

Measured memory_bytes: 7044