#include <iostream>
#include <cstdlib>
#include <vector>
#include <algorithm>
#include <cmath>
int main()
{
    int a;
    std::string s, t;
    std::cin >> a >> s >> t;
    int c = 0;
    for(int i = 0; i < a; i++){
        if(s[i] != t[i]) c++;
    }
    std::cout << c << std::endl;
    return 0;
}