#include<fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
long long n,rez;
int a[1000005];
int main(){
    in >>n;
    for (int  i = 2; i <= n; i++){
        a[i] = i;

    }
    for (int i = 2; i <= n; i++){
        if (a[i] == i)
        {
            for(int j = i; j <= n; j+=i){
                a[j]/=i;
                a[j]*=(i-1);
            }
        }
    }
    for(int i = 2; i <= n; i++){
        rez+=a[i];
    }
    out << 2*rez + 1;
}