#include<fstream>
using namespace std;
long long n,s,i,j,a[1000010];
long cmmdc(long a, long b)
{
 if(b==0)
  return a;
 return cmmdc(b,a%b);   
}
int main()
{
 ifstream f("fractii.in");
 ofstream g("fractii.out");
 
 f>>n;
 s=1;
 for(i=2;i<=n;i++)
  a[i]=i-1;
 for(j=2;j<=n;j++)
 {
  for(i=2*j;i<=n;i+=j)                 
   a[i]-=a[j];
  s+=a[j];
 }
 
 
 g<<2*s-1;
 
 
 
 f.close();
 g.close();
 return 0;   
}