#include<iostream>
#include<fstream>
#include<sstream>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<vector>
#include<list>
#include<algorithm>
#include<utility>
#include<complex>
#include<functional>
using namespace std;


#define input_init stringstream ss; string strtoken, token; istringstream is
#define input_line  getline(cin, strtoken);is.str(strtoken);is.clear(istringstream::goodbit)
#define input_token(num) ss.str(""); ss.clear(stringstream::goodbit); getline(is, token, ','); ss << token; ss >> num



int main(void){
	int n,m;
	string s;
	string t;
	cin >> n>>m >> s >> t;
	vector<vector<int>> dp(n + 2, vector<int>(m + 2, 10000));
	dp[0][0] = 0;

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