#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");

int n, sol[1000004];
long long sum;

int main()
{ int s=0,i,j;
  in>>n;
  for(i=2;i<=n;i++)
    {sol[i]=i-1;}
  for (i=2;i<=n;i++)
    {sum+=sol[i];
    for(j=2*i;j<=n;j+=i)
     {sol[j]=sol[j]-sol[i];}
    }
  out<<sum*2+1;
  in.close();
  out.close();
  return 0;
}