#include<fstream> 
using namespace std; 
long v[1000001]; 
int main() 
{ 
    long long i,j,n,nr=0;   
    ifstream cin ("fractii.in") ;
    ofstream cout ("fractii.out");
    cin>>n;
   
   for(i=2;i<=n;i++) 
   v[i]=i-1; 
   
   for(i=2;i<=n;i++) 
{ 
                     for(j=i+i;j<=n;j+=i) 
                     v[j]-=v[i];
                     nr+=v[i]; 
} 
  nr=nr*2+1; 
  
  cout<<nr; 
  cin.close(); 
  cout.close(); 
  return 0; 
}