#include <fstream.h>  
 #include <math.h>  
 int main ()  
 { long v[1000001],p,e,y,n,z,i,j,x,nrf;  
 long long nr,rad;  
 ifstream f("fractii.in");  
 ofstream g("fractii.out");  
 f>>n;  
 v[1]=1;  
 for (i=2;i<=n;i++)  
	 { x=i;  
     p=2;  
     z=1;  
     rad=sqrt(x);  
     while (p<=rad && x%p>=1) p++;  
     if (p>rad) v[i]=i-1;  
     else {  
       y=x;  
       e=0;  
      while (y%p==0)  
         { 
			 y/=p;  
			 e++;  
			 z=z*p;  
        }  
	z=z/p;  
	v[x]=v[y]*(p-1)*z;  
    }}  
 nr=1;  
 for (i=2;i<=n;i++)  
	nr=nr+2*v[i];  
 g<<nr;  
 f.close();  
 g.close();  
 return 0;  
 }