#include<stdio.h>
#include<math.h>
int phi[1000005];
void ciur ( int n)
{
	int i,j,lim;
	for(i=1;i<=n;phi[i]=i,i++);
	for(i=2;i<=n;i++)
		if(phi[i]==i)
			for(j=i;j<=n;j=j+i)
					phi[j]=phi[j]/i*(i-1);
}

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