import math
import sys
from typing import List, Tuple


def int1(x: str, /): return int(x) - 1


def input(): return sys.stdin.readline().rstrip('\n')


def dbg(*args, **kwargs):
    print(*(repr(arg) for arg in args), *(f'{k}: {repr(v)}' for k, v in kwargs.items()), sep='; ', file=sys.stderr)


def main():
    n, m = map(int, input().split())
    s = '$' + input()
    t = '$' + input()
    d = [[math.inf] * (m + 1) for _ in range(n + 1)]
    d[0][0] = 0
    for i in range(n+1):
        for j in range(m+1):
            if i > 0:
                d[i][j] = min(d[i][j], d[i - 1][j] + 1)
            if j > 0:
                d[i][j] = min(d[i][j], d[i][j - 1] + 1)
            if i > 0 and j > 0:
                d[i][j] = min(d[i][j], d[i - 1][j - 1] + (1 if s[i] != t[j] else 0))
    return d[-1][-1]


def _start():
    ret = main()

    if ret is not None:
        if isinstance(ret, List) or isinstance(ret, Tuple):
            print(*ret)
        else:
            print(ret)


if __name__ == '__main__':
    _start()