#include <bits/stdc++.h>
using namespace std;

int n,m;
char s[1001],t[1001];

int dp[1001][1001];

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

	for(int i=0;i<=n;++i){
		for(int j=0;j<=m;++j){
			if(i==0){
				dp[i][j]=j;
			}else if(j==0){
				dp[i][j]=i;
			}else if(s[i-1]==t[j-1]){
				dp[i][j]=dp[i-1][j-1];
			}else{
				dp[i][j]=min(dp[i-1][j-1],min(dp[i-1][j],dp[i][j-1]))+1;
			}
		}
	}

	cout << dp[n][m] << endl;

	return 0;
}