#include <iostream>
#include <string>

int main(){
    int n;
    std::cin >> n;
    std::string S;
    std::string T;
    std::cin >> S >> T;
    int count = 0;
    for(int i = 0;i < n;i++){
        if (S[i] != T[i]) {
			count++;
		}
    }
    std::cout << count << std::endl;
    return 0;
}