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