//No.224 文字列変更(easy)
#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main(){
    int n; cin >> n;
    string s , t; cin >> s >> t;
    int cnt = 0;
    for ( int i = 0 ; i < n ; ++i){
        if( s[i] != t[i]) ++cnt;
    }
    cout << cnt << endl;
}