#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int V[1000000], N;
long long count;
 
int main()
{
    
   in>>N;
   for(int i=1;i<=N;i++) V[i] = i-1;
   for(int i=2;i<=N;i++)
   {
       for(int j=(i<<1);j<=N;j+=i)
       {
          V[j]-=V[i];
       }
       count+=V[i];
    }
 
  count<<=1;
  out<<++count<<"\n";
  out.close();
 
  return 0;
}