#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <stdio.h>
#include <string.h>
using namespace std;

int main() {
    int n;
    string s, t;
    cin >> n >> s >> t;

    int r = 0;
    for (int i = 0; i < n; i++) {
        if (s[i] != t[i]) r++;
    }
    cout << r << endl;

    return 0;
}