#include <iostream>
#include <string>

using namespace std;

int main() {
	int n;
	string s, t;
	cin >> n >> s >> t;
	int result = 0;
	for (size_t i = 0; i < s.size(); ++i) {
		if (s[i] != t[i]) {
			++result;
		}
	}
	cout << result << endl;
	return 0;
}