#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
#include <algorithm>
#include <string>
#include <map>
#include <iterator>
#include <set>
#include <queue>

using namespace std;


int main() {

    int n;
    cin >> n;
    string S, T;
    cin >> S >> T;

    int cnt = 0;
    for (int i = 0; i < n; ++i) {
        if(S[i] != T[i]) {
            cnt += 1;
        }
    }

    cout << cnt << endl;


    return 0;
}