#include<fstream.h>
#include<math.h>
int main()
{
long i,n,x,d,y,l,rad,j,nr;
long long a[1000000];
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;
	y=x;
rad=sqrt(x);
	while (d<=rad&&x/d>0) d++;
	if (d>rad) a[i]=i-1;
	else {
		l=1;
		while (y%d==0)
			{
			y=y /d;
			l=l*d;
			}
		l=l / d;
		a[i]=a[y]*(d-1)*1;
		}
	nr=nr+2*a[i];
	}
	g<<nr;
	return 0;
	}