#include<cstdio>
#include<cmath>
#include<cstring>
#include<ctime>
#include<iostream>
#include<algorithm>
#include<set>
#include<vector>
#include<sstream>
#include<typeinfo>
#include<fstream>

using namespace std;

int n, m;

char s[1001],t[1001];

int dp[1001][1001];



/*void solve(){
	for (int i = 0; i <= n; ++i){
		for (int j = 0; j <= m; ++j){
			if (i == 0){
				dp[i][j] = j;
				continue;
			}
			if (j == 0){
				dp[i][j] = i;
				continue;
			}
			//dp[i][j]=1000000;
			if (s[i] != t[j]){
				dp[i + 1][j + 1] = min(dp[i][j + 1] + 1, min(dp[i + 1][j] + 1, dp[i][j]));
			}
			else if (s[i] == t[j]){
				dp[i + 1][j + 1] = min(dp[i][j], min(dp[i][j + 1] + 1, dp[i + 1][j] + 1));
			}

			//dp[i+1][j+1]=min(dp[i+1][j+1],dp[i][j+1]+1);

			//dp[i+1][j+1]= min(dp[i+1][j+1],dp[i+1][j]+1);

		}
	}

}*/

int main(){

	cin >> n >> m >> s >> t;
	/*for (int i = 0; i<n; i++){
		cin >> s[i];
		}
		for (int i = 0; i<m; i++){
		cin >> t[i];
		}*/

	//solve();
	for (int i = 0; i <= n; ++i){
		for (int j = 0; j <= m; ++j){
			if (i == 0){
				dp[i][j] = j;
				continue;
			}
			if (j == 0){
				dp[i][j] = i;
				continue;
			}

			//dp[i][j]=1000000;
			if (s[i - 1] != t[j - 1]){
				dp[i][j] = min(dp[i - 1][j] + 1, min(dp[i][j - 1] + 1, dp[i - 1][j - 1] + 1));
			}
			else if (s[i - 1] == t[j - 1]){
				dp[i][j] = dp[i - 1][j - 1];
			}

			//dp[i+1][j+1]=min(dp[i+1][j+1],dp[i][j+1]+1);

			//dp[i+1][j+1]= min(dp[i+1][j+1],dp[i+1][j]+1);

		}
	}

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

	return 0;
}