#include <fstream>
#include <iostream>

std::ifstream f("fractii.in");
std::ofstream g("fractii.out");

static const int mLen = 1000005;
int e[mLen];

int main()
{
	int n;
	f >> n;
	e[1] = 1;
	for (int i = 2; i < mLen; i++)
	{
		e[i] = i;
	}
	for (int i = 2; i < mLen; i++)
	{
		if (e[i] == i)
		{
			for (int j = i; j < mLen; j += i)
			{
				e[j] = e[j] / i * (i - 1);
			}
		}
	}

	long long s = 0;
	for (int i = 1; i <= n; i++)
	{
		s = s + e[i];
	}
	g << 2 * s - 1;
}