import sys
import math
import bisect
from heapq import heapify, heappop, heappush
from collections import deque, defaultdict, Counter
from functools import lru_cache
from itertools import accumulate, combinations, permutations, product

sys.set_int_max_str_digits(10 ** 6)
sys.setrecursionlimit(1000000)
MOD = 10 ** 9 + 7
MOD99 = 998244353

input = lambda: sys.stdin.readline().strip()
NI = lambda: int(input())
NMI = lambda: map(int, input().split())
NLI = lambda: list(NMI())
SI = lambda: input()
SMI = lambda: input().split()
SLI = lambda: list(SMI())
EI = lambda m: [NLI() for _ in range(m)]


def edit_distance(S, T):
    N = len(S)
    M = len(T)

    INF = N + M + 2
    dp = [[INF] * (M + 1) for _ in range(N + 1)]
    for i in range(N + 1):
        dp[i][-1] = N - i
    for j in range(M + 1):
        dp[-1][j] = M - j

    for i in range(N - 1, -1, -1):
        s = S[i]
        for j in range(M - 1, -1, -1):
            t = T[j]

            dp[i][j] = min(
                dp[i + 1][j] + 1, dp[i][j + 1] + 1, dp[i + 1][j + 1] + int(s != t)
            )

    return dp[0][0]


def main():
    N, M = NMI()
    print(edit_distance(SI(), SI()))


if __name__ == "__main__":
    main()