#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
int dp[1010][1010];
int main() {
	int n, m;
	cin >> n >> m;
	string s, t;
	cin >> s >> t;
	for (int i = 0; i <= n; i++) {
		dp[i][0] = i;
	}
	for (int i = 0; i <= m; i++) {
		dp[0][i] = i;
	}
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			dp[i][j] = min({ dp[i - 1][j] + 1,dp[i][j - 1] + 1,dp[i - 1][j - 1] + (s[i] != t[j]) });
		}
	}
	cout << dp[n][m] << endl;
}