#include<stdio.h>

#define dim 1000001

long long unsigned n,x[dim],i,j,s;

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



	scanf("%llu",&n);

	s=0;

	for(i=1;i<=n;i++)

	{	if(x[i]==0)

		{	s+=i-1;

			for(j=2*i;j<=n;j+=i)

				if(x[j]==0)

					x[j]=j-j/i;

				else

					x[j]=x[j]-x[j]/i;

		}

		else

			s+=x[i];

   }

		printf("%llu ",2*s+1);

	return 0;
}