#include <algorithm>
using namespace std;
#define rep(i,b) for(int i=0;i<b;i++)

template<class String>
int LevenshteinDistance(String const & s, String const & t){
    static int dp[2048][2048]; // 16 MB
    int n = s.size(), m = t.size();
    rep(i,n+1) dp[i][0] = i;
    rep(i,m+1) dp[0][i] = i;
    rep(i,n)rep(j,m){
        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] + (s[i]!=t[j]));
    }
    return dp[n][m];
}

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