#include<stdio.h>
int n,i,j,s[1000005];
long long int t;
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&n);
	for(i=2;i<=n;i++)
		s[i]=i-1;
	for(i=2;i<=n;i++)
	{
		t+=s[i];
		for(j=i+i;j<=n;j+=i)
			s[j]-=s[i];
	}
	printf("%lld",2*t+1);
}