#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;