#include<iostream.h>
#include<fstream>
	ifstream f("fractii.in");
	ofstream g("fractii.out");
int main()
{	
	long long k,n,x[1000001],i,m=0;
	f>>n;
	f.close();
	for(i=2;i<=n;i++)
		x[i]=i-1;
	for(i=2;i<=n;i++)
	{
		m+=x[i];
		for(k=2*i;k<=n;k+=i)
			x[k]-=x[i];
	}
	g<<m*2+1;
	g.close();
	return 0;
}