#include <fstream>
#define NMAX 1000002
using namespace std;

int main()
{
	int n, prim[NMAX], i, j;
	long long rez = 1;
	ifstream f("fractii.in");
	f >> n;
	f.close();
	for (i = 1; i <= n; i++)
	{
		prim[i] = i - 1;
	}
	for (i = 2; i <= n; i++)
	{
		for (j = i + i; j <= n; j += i)
		{
			prim[j] = prim[j] - prim[i];
		}
	}
	for (i = 2; i <= n; i++)
	{
		rez += 2LL * (long long)prim[i];
	}
	ofstream g("fractii.out");
	g << rez;
	g.close();
	return 0;
}