#include <bits/stdc++.h>

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]) ans++;
    }
    cout << ans << endl;
    return 0;
}