#include<fstream.h>  
#include<math.h>  
long a[1000001],n,i,ii,j,x,y,q,m,ok;
long long nr,r;  
int main()  
{  
ifstream f("fractii.in");  
ofstream g("fractii.out");  
f>>n;  
a[1]=1;  
for(i=2;i<=n;i++)  
 {x=i;  
 q=2;  
r=sqrt(x);  
while(q<=r && x%q)q++;  
 if(q>r)a[i]=i-1;  

 else  
 {  
 y=1;  
while(x%q==0){y=y*q;  
  x=x/q;  
  }  
 y=y/q;  
 a[i]=(q-1)*y*a[x];  
 }  
   
 }  
  nr=1;  
 for(i=2;i<=n;i++)  
   nr=nr+2*a[i];  
   g<<nr;  
  g.close();  
    return 0;  
}