#include <iostream>
#include <fstream>
using namespace std;
int main(){
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    long n;
    long long sum = 0;
    f>>n;
    long a[n+1];
    long i,j;
    for (i=2;i<=n;i++)
        a[i]=i-1;

    for (i=2;i<=n;i++)
    {
        sum+=a[i];
        for (j=2*i;j<=n;j+=i)
            a[j]-=a[i];
    }
   g<<2*sum+1;
   f.close();
   g.close();
   return 0;
}