#include <iostream>
#include <vector>
#include <string>
#include <cmath>
#include <iomanip>
using namespace std;
using ll = long long;

int main() {
    int N;
    cin >> N;
    string s1, s2;
    cin >> s1 >> s2;
    int res = 0;
    for(int i=0; i<N; ++i) {
        res += s1[i] != s2[i];
    }
    cout << res << endl;
}