#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>

using namespace std;

int main() {
	int n;
	string s, t;

	cin >> n >> s >> t;

	int diff = 0;
	for (int i = 0; i < n; i++) {
		if (s[i] != t[i]) {
			diff++;
		}
	}

	cout << diff << endl;
	return 0;
}