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