#include <fstream>
#define p 1000005
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n, a[p];
long long function(int n)
{
	long long s = 1;
	for (int i = 2; i <= n; i++)
		a[i] = i - 1;
	for (int i = 2; i <= n; i++)
	{
		s += 2 * a[i];
		for (int j =2 * i; j <= n; j += i)
			a[j] -= a[i];
	}
	return s;
}
int main()
{
	f >> n;
	g << function(n);
}