#include<iostream>
#include<fstream>

using namespace std;

ifstream fin("fractii.in ");
ofstream fout("fractii.out");

unsigned phi[1000001];

int main()
{
   long long  n;
   fin>>n;


for (long i=1;i<=n;i++) phi[i]=i;
   for (long i=2;i<=n;i++)
      if (phi[i]==i)
         for (long j=i;j<=n;j+=i) phi[j] /=i, phi[j] *= (i-1);

   long long s=1;

   for(int i=1;i<=n;i++)
   {
      s+=phi[i]*2;
   }
   fout<<s;
fout.close();
return 0;

}