#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;
    scanf("%d%d%s%s", &n, &m, s, t);

    short dp[2][1001], *dp0 = dp[0], *dp1 = dp[1];
    for (int j = 0; j <= m; j++) {
        dp0[j] = j;
    }
    for (int i = 0; i < n; i++) {
        swap(dp0, dp1);
        dp0[0] = i + 1;
        for (int j = 0; j < m; j++) {
            dp0[j + 1] = min(min(dp0[j], dp1[j + 1]) + 1, dp1[j] + (s[i] != t[j]));
        }
    }
    printf("%d\n", dp0[m]);

    return 0;
}