#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
	int n, m;
	cin >> n >> m;
	string s, t;
	cin >> s >> t;
	vector<vector<int>> dp(n + 1, vector<int>(m, 1001));
	dp[0][0] = 0;
	for (int i = 1; i <= n; i++) {
		for (int j = 0; j < m; j++) {
			if (j == 0) {
				if (s[i - 1] == t[j]) {
					dp[i][j] = dp[i - 1][j];
				}
				else {
					dp[i][j] = dp[i - 1][j] + 1;
				}
			}
			else {
				if (s[i - 1] == t[j]) {
					dp[i][j] = min(dp[i - 1][j - 1], min(dp[i - 1][j] + 1, dp[i][j - 1] + 1));
				}
				else {
					dp[i][j] = min(dp[i - 1][j - 1] + 1, min(dp[i - 1][j] + 1, dp[i][j - 1] + 1));
				}
			}
		}
	}
	cout << dp[n][m - 1] << endl;
}