#include <bits/stdc++.h>
#define rep(i, z, n) for(int i = z; i < n; i++)
#define all(v) v.begin(), v.end()
typedef long long ll;
const int INF = 1<<29;
using namespace std;

int main(){
    int a,b;
    cin >> a >> b;
    string S, T;
    cin >> S >> T;
    vector<vector<int>> dp(S.size() + 1, vector<int>(T.size() + 1, 0));
    rep(i, 0, S.size() + 1) dp[i][0] = i;
    rep(i, 1, T.size() + 1) dp[0][i] = i;
    
    rep(i, 0, S.size()){
        rep(j, 0, T.size()){
            if (S[i] != T[j]) {
                dp[i+1][j+1] = min(min(dp[i+1][j],dp[i][j+1]), dp[i][j]) + 1;
                //cout << dp[i+1][j+1] << endl;
            }
            else dp[i+1][j+1] = dp[i][j];
        }
    }
    cout << dp[S.size()][T.size()] << endl;
}