#include <stdio.h>
int a[50],b[50];

int phi(int m)
{
	int s,q;
	q=1;
	for(s=2;s*s<=m;s++)
	{
		if (m%s==0)
		{
			q=q*(s-1);
			m=m/s;
			whlie (m%s==0)
			{
				q=q*s;
				m=m/s;
			}
		}
	}
	if (m!=0) 
		q=q*(m-1);
	return q;
}

int main()
{
	int n,k;
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",n);
	for (int i=2;i<=n;i++)
		nr=nr+phi(i);		
	nr=nr*2;
	return 0;
}