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