#include<iostream.h>  
#include<fstream.h>  
#include<math.h>  
   
 int main()  
     {  
     fstream f("fractii.in",ios::in),g("fractii.out",ios::out);  
     long long i,j,nr,phi,n,rez=1;long double radpat;  
     f>>n;  
     for(i=2;i<=n;i++)  
         {  
         nr=i;phi=i;
         radpat=sqrt(nr);  
         for(j=2;j<=radpat;j++)  
             {  
             if(nr%j==0)  
                 {  
                 phi=phi*(j-1)/j;  
                 while(nr%j==0)  
                     nr/=j;  
                 }  
             }  
         if(nr>1)  
             phi=phi*(nr-1)/nr;  
         rez+=2*phi;  
         }  
     g<<rez;  
     f.close();  
     g.close();  
     return 0;  
     }