#include <iostream>
#include <algorithm>
#include <vector>
#include <string.h>
using namespace std;

int n, m;
string S, T;

int dp[1010][1010];

int choose(int s_now, int t_now){
    if(dp[s_now][t_now] != -1){
        return dp[s_now][t_now];
    }else if(s_now == n){
        return dp[s_now][t_now] = m - t_now;
    }else if(t_now == m){
        return dp[s_now][t_now] = n - s_now;
    }else if(S[s_now] == T[t_now]){
        return dp[s_now][t_now] = choose(s_now + 1, t_now + 1);
    }else{
        return dp[s_now][t_now] = min({choose(s_now, t_now + 1) + 1, choose(s_now + 1, t_now) + 1, choose(s_now + 1, t_now + 1) + 1});
    }
}

int main(){
    cin >> n >> m >> S >> T;
    memset(dp, -1, sizeof(dp));
    cout << choose(0, 0) << endl;
}