#include <iostream>

int main(){
    int N;
    std::cin >> N;

    std::string S, T;
    std::cin >> S >> T;

    int diff = 0;
    for(int i=0;i<N;i++){
        if(S[i] != T[i]){diff += 1;}
    }

    std::cout << diff << std::endl;
}