#include<stdio.h>
int e[1000001],n,i,j,z,s;
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	s=0;
	scanf("%d",&n);
	for(i=1;i<=n;++i)
	{
		e[i]=i;
	}
	for(i=2;i<=n;i++)
	{
		if(e[i]==i)
		{
			for(j=i;j<=n;j=j+i)
			{
				e[j]=e[j]/i*(i-1);
			}
		}
	}
	for(i=1;i<=n;i++)
	{
		s=s+e[i];
	    z=s*2-1;
	}
	printf("%d",z);
	return 0;
}