#include <iostream>
#include <string>

using namespace std;

int main() {

    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    int n;
    cin >> n;
    string s, t;
    cin >> s >> t;

    int count = 0;
    for (int i = 0; i < n; ++i) {
        if (s.at(i) != t.at(i)) count++;
    }
    cout << count << endl;
    return 0;
}