#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;    
 }