#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main(){
    string s1,s2;
    int n,count=0;
    cin >> n >> s1 >> s2;
    for(int i=0;i<n;i++){
        if(s1[i]!=s2[i])    count++;
    }
    cout << count;
    return 0;
}