#include <iostream>
#include <cstdlib>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
int main(){
    int n; string S, T; cin >> n >> S >> T;
    int cnt = 0;
    for(int i = 0; i < n; i++){
        if(S[i] != T[i]) cnt++;
    }
    cout << cnt << endl;
}