// http://infoarena.ro/problema/fractii stare:  punctaj: 
#include <fstream.h>
#define nmax 30000
ifstream fin("fractii.in");
ofstream fout("fractii.out");

int phi[nmax],n;

int main()
{
 fin>>n;
 for (int i=1;i<=n;i++) phi[i]=i;
 for (i=2;i<=n;i++)
   if (phi[i]==i)
      for (int j=i;j<=n;j+=i)
   			phi[j]=phi[j]/i*(i-1);
 long long num=1;  
    for (i=2; i<=n; ++i)  
			num+=phi [i]*2;  
  fout<<num;

		 return 0;
}