#include<fstream.h>      
  #include<math.h>      
  long a[2000000],n,i,ii,j,x,y,p,m,ok;  
 long long nr,rad;
 int main()      
  {      
  ifstream f("fractii.in");      
 ofstream g("fractii.out");      
  f>>n;      
  a[1]=1;      
  for(i=2;i<=n;i++)      
   {  x=i;  
      p=2;  
      rad=sqrt(x);  
      while(p<=rad && x%p)  
         p++;  
      if(p>rad)  
         a[i]=i-1;  
   
      else  
      {  
         y=1;  
         while(x%p==0)  
            { y=y*p;  
             x=x/p;  
            }  
         y=y/p;  
         a[i]=(p-1)*y*a[x];  
   
      }  
        
   }      
    nr=1;      
   for(i=2;i<=n;i++)          
     nr=nr+2*a[i];  
 g<<nr;      
 g.close();      
 return 0;      
  }