#include<iostream>
#include<string>

int main() {
	int length;
	std::string str, str2; 

	std::cin >> length >> str >> str2;

	int count = 0;
	for (int i = 0; i < length; i++) {
		if (str[i] != str2[i]) count++;
	}

	std::cout << count << std::endl;

	return 0;
}