#include <iostream>

using namespace std;

int main() {
    int n;
    string s, t;
    
    cin >> n >> s >> t;
    
    int ct = 0;
    for (int i = 0; i < n; i++) {
        if (s[i] != t[i]) {
            ct++;
        }
    }
    
    cout << ct << endl;
    
    return 0;
}