#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int weighted_levenshtein(string &a, string &b, int _insert = 1, int _delete = 1, int _substitute = 1){
    int len_a = a.size(), len_b = b.size();
    vector<vector<int>> dp(len_a + 1, vector<int> (len_b + 1, 0));
    for(int i = 0; i < len_a + 1; i++) dp[i][0] = i * _delete;
    for(int j = 0; j < len_b + 1; j++) dp[0][j] = j * _insert;
    for(int i = 1; i < len_a + 1; i++){
        for(int j = 1; j < len_b + 1; j++){
            int x = (a[i - 1] == b[j - 1] ? 0 : _substitute);
            dp[i][j] = min({dp[i - 1][j] + _delete,
                            dp[i][j - 1] + _insert,
                            dp[i - 1][j - 1] + x});
       }
    }
    return dp[len_a][len_b];
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int n,m; cin >> n >> m;
    string S,T; cin >> S >> T;
    cout << weighted_levenshtein(S, T, 1, 1, 1) << "\n";
}