#include <fstream.h>


ifstream f("fractii.in");
ofstream g("fractii.out");




int n;


void citire()
{
    f>>n;     
    f.close();
}



    
long phi[1000001];
long long nr=0LL;


int main()
{
    
      long i,j;
      citire();
      for (i=1;i<=n;i++)
         phi[i]=i-1;
      for (i=2;i<=n;i++)
        for (j=i+i;j<=n;j=j+i)
           phi[j]=phi[j]-phi[i];
      for (i=1;i<=n;i++)
        nr=nr+phi[i];
      nr=2*nr+1;
      g<<nr;  
}