#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
#include<set>
#include<bitset>
#include<math.h>
#include<map>
#include<queue>
#include<iomanip>
using namespace std;

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