#include <bits/stdc++.h>
using ll = long long;
using llu = long long unsigned;

using namespace std;

int main() {
    int n;
    string S, T;
    cin >> n >> S >> T;

    int result = 0;
    for (int i=0; i<n; i++) {
        if (S[i]!=T[i]) { result++; }
    }
    cout << result << endl; return 0;
}