#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n,phi[1000005];
long long sol;
int main()
{ int i,j;
    f>>n;
   for (int i=1;i<=n;i++) phi[i]=i;

  for (int i=2;i<=n;i++)
   {if (phi[i]==i)
      for (j=i;j<=n;j+=i) phi[j] /=i, phi[j] *= (i-1);
   sol+=phi[i];
   }
   g<<2*sol+1;
    return 0;
}