#include<stdio.h>

int n,i,j,v[1000000];
long long nr,p1,p2;

int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);

	scanf("%d",&n);

	for(i=2;i<=n;i++)
		v[i]=i-1;

	for(i=2;i<=n;i++)
	{
		nr+=v[i];

		for(j=2*i;j<=n;j+=i)
			v[j]-=v[i];
	}

	printf("%lld",nr*2+1);

	return 0;
}