#include <iostream>
using namespace std;
int main(void) {
	int n;
	string s, t;
	cin >> n >> s >> t;
	int ans = 0;
	for (int i = 0; i < n; ++i) {
		if (s[i] != t[i]) ++ans;
	}
	cout << ans << endl;
	return 0;
}