#include<stdio.h>
long n;
long e[1000010];

void ciur()
{
	long i,j;
	for(i=2;i<=n;i++)
		e[i]=i;
	for(i=2;i<=n;i++)
		if(e[i]==i)//i este prim
		{
			for(j=i;j<=n;j+=i)
				e[j]=e[j]/i*(i-1);
		}
}

int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%ld",&n);
	ciur();
	long i,s=0;
	for(i=2;i<=n;i++)
		s=s+2*e[i];
	printf("%ld\n",s+1);
	return 0;
}