#include<iostream>
    #include <string>
    using namespace std;
    int main(){

    int n;
    string s;
    string s2;
    cin>>n;
    cin>>s;
    cin>>s2;

    int count = 0;

    for(int i = 0; i<n; i++){

        if(s[i] != s2[i]){
            count ++;



        }
    }
    cout<<count;



        return 0;
    }