#include<fstream.h>    
 #include<math.h>    
 long a[1000001],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;
f.close();    
g.close();    
return 0;    
 }