#include<fstream>
using namespace std;
long long max1=0;
int n,i,j,nr[1000001];
int main()
{
	ifstream f("fractii.in");
	ofstream g("fractii.out");
	f>>n;
	for(i=2;i<=n;i++)
		nr[i]=i-1;
	for(i=2;i<=n;i++)
	{
		max1+=nr[i];
		for(j=i+i;j<=n;j=j+i)
			nr[j]-=nr[i];
	}
	max1=max1*2+1;
	g<<max1;
	return 0;
}