#include<stdio.h>
int n,i,j;
int e[1000010];
long long s;
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&n);	
	for(i=2;i<=n;i++)
		e[i]=i;
	for(i=2;i<=n;++i)
		if(e[i]==i)
		{
			for(j=i;j<=n;j+=i)
				e[j]=e[j]/i*(i-1);
		}
	s=0;
	for(i=2;i<=n;i++)
		s=s+(long long)e[i];
	printf("%lld",2*s+1);
	return 0;
}