#include <algorithm>
#include <cmath>
#include <iostream>
#include <vector>
using namespace std;

int main() {
    int n;
    string S, T;
    cin >> n >> S >> T;
    int ans = 0;
    for (int i = 0; i < n; i++) {
        if ((S[i] - T[i]) != 0) ans++;
    }
    cout << ans << endl;

    return 0;
}