#include<iostream>
#include<fstream>
using namespace std;
long long n,i,s=0,p,t;
int a[1000001];

int main()
{
	ifstream f("fractii.in");
	ofstream g("fractii.out");
	
	
	
	f>>n;
	for(i=2;i<=n;i++)
	   a[i]=i-1;
	
	
	for(i=2;i<=n;i++)
	{
	t=2;
	p=t*i;
	s=s+a[i];
		while(p<=n)
		{
			
			
			a[p]=a[p]-a[i];
			t++;
			p=t*i;
			
		}
	}
	
	
         g<<2*s+1;
		 return 0;
		 
}