#include <fstream>
using namespace std;
unsigned long long phi[1000001];
int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    unsigned long long n,nrf=0,i,j;
    f>>n;
    for ( i = 1; i <= n; ++i)
        phi[i] = i-1;
    for ( i = 2; i <= n; ++i)
    {
        nrf+=phi[i];
        for ( j = 2*i; j <= n; j += i)
            phi[j] -= phi[i];
    }
    g<<2*nrf+1<<'\n';
    f.close();
    g.close();
    return 0;

}