#include<stdio.h>
int i,j,v[1000100],n;
long long s;
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&n);
	for(i=1;i<=n;i++)
		v[i]=i;
	for(i=2;i<=n;i++)
	{
		if(v[i]==i)
		{
			for(j=i;j<=n;j+=i)
			{
				v[j]=v[j]*(i-1)/i;
			}
		}
	}
	for(i=2;i<=n;i++)
		s=s+v[i];
	s=s*2;
	s++;
	printf("%lld",s);
	return 0;
}