#include<fstream>   
using namespace std;   
long n,s,i,j,a[1000000];   
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;      
}