#include <algorithm>
using namespace std;
#define rep(i,b) for(int i=0;i<b;i++)
int LevenshteinDistance(const string& str1, const string& str2){
    static int dp[2048][2048]; // 16 MB
    int l1 = str1.size(), l2 = str2.size();
    rep(i,l1+1) dp[i][0] = i;
    rep(i,l2+1) dp[0][i] = i;
    rep(i,l1)rep(j,l2){
        dp[i+1][j+1] = min(dp[i][j+1], dp[i+1][j]) + 1;
        dp[i+1][j+1] = min(dp[i+1][j+1], dp[i][j] + (str1[i]!=str2[j]));
    }
    return dp[l1][l2];
}

#include <iostream>
int main(){
    int n,m;
    string s,t;
    cin >> n >> m >> s >> t;
    cout << LevenshteinDistance(s,t) << endl;
}