#include <fstream>

using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");
int phi[1000010],n;
long long s=0;

void Phi()
{
	for (int i = 1;i <= 1000010;i++)
		phi[i] = i - 1;
	for (int i = 2;i <= 1000010;i++)
		for (int j = 2 * i;j <= 1000010;j += i)
			phi[j] -= phi[i];
}

long long Number_of_fractions(int n)
{
	for (int i = 1;i <= n;i++)
		s += phi[i];
	return 2 * s + 1;
}

int main()
{
	Phi();
	f >> n;
	g << Number_of_fractions(n) << "\n";
	f.close();
	g.close();
	return 0;
}