#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
long long V[1000000], N, 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;
}