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