#include <fstream>

using namespace std;

ifstream f ("fractii.in");
ofstream g ("fractii.out");

int phi(int x)
{
  long long rez = x;
  int i;
   for (i=2; i*i<=x; i++)
   {
       if (x % i == 0)
       {
            while (x % i == 0)
                x /= i;
         rez = (rez / i) * (i - 1);
       }
   }
  if (x > 1)
    rez = (rez / x) * (x - 1);
  return rez;
}

int i, n;
long long rez;

int main()
{
 f >> n;
 rez = 1;
  for (i=2; i<=n; i++)
    rez += 2 * phi(i);
  g << rez;
    return 0;
}