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

int main() {
    int n, m;
    string s, t;
    cin >> n >> m >> s >> t;

    vector<vector<int>> dp(n + 1, vector<int>(m + 1));
    for (int j = 0; j <= m; j++) {
        dp[0][j] = j;
    }
    for (int i = 1; i <= n; i++) {
        dp[i][0] = i;
        for (int j = 1; j <= m; j++) {
            dp[i][j] = min(min(dp[i][j - 1], dp[i - 1][j]) + 1, dp[i - 1][j - 1] + (s[i - 1] != t[j - 1]));
        }
    }
    cout << dp[n][m] << endl;

    return 0;
}