#include <bits/stdc++.h>
using namespace std;

int N, M;
string S, T;

vector<vector<int>> memo;

int book(int s, int t) {
    if (s == 0 && t == 0)
        return 0;
    if (s < 0 || t < 0)
        return 1e5;
    if (memo[s][t] != -1)
        return memo[s][t];
    int& ret = memo[s][t];
    ret = 1e5;
    ret = min(ret, book(s - 1, t - 1) + (S[s - 1] != T[t - 1]));
    ret = min(ret, book(s - 1, t) + 1);
    ret = min(ret, book(s, t - 1) + 1);
    return ret;
}

int main() {
    cin >> N >> M >> S >> T;
    memo.resize(N + 1);
    for (int i = 0; i < N + 1; i++)
        memo[i].resize(M + 1, -1);
    cout << book(N, M) << endl;
}