#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <stdio.h>
#include <string.h>
using namespace std;

int main() {
    char s[1001], t[1001];
    int n, m;
    cin >> n >> m >> s >> t;

    int dp[2][1001], *dp0 = dp[0], *dp1 = dp[1];
    for (int j = 0; j <= m; j++) {
        dp0[j] = j;
    }
    for (int i = 1; i <= n; i++) {
        swap(dp0, dp1);
        dp0[0] = i;
        for (int j = 1; j <= m; j++) {
            dp0[j] = min(min(dp0[j - 1], dp1[j]) + 1, dp1[j - 1] + (s[i - 1] != t[j - 1]));
        }
    }
    cout << dp0[m] << endl;

    return 0;
}