#include<iostream>
#include<algorithm>
#include <vector>
#include<cmath>
#include<iomanip>
using namespace std;
typedef long long int lont;
int main() {
	int N;
	string S, T;
	cin >> N >> S >> T;
	int cnt = 0;
	for (int ia = 0; ia < N; ia++) {
		if (S.at(ia) == T.at(ia)) {
			cnt++;
		}
	}
	cout << N - cnt << endl;
}