#include <iostream>
#include <fstream>
#define nmax 1000005
using namespace std;

ifstream in("fractii.in");
ofstream out("fractii.out");

int n, sol;
int v[nmax];

int main() 
{
	cin >> n;
	for (int i = 1; i <= n; v[i] = i,++i);
	for (int i = 2; i <= n; ++i)
	{
		--v[i];
		for (int j = 2 * i; j <= n; j += i)
			v[j] -= v[i];
	}
	for (int i = 1; i <= n; sol += 2 * v[i],++i);
	cout << sol - 1;
	system("pause");
}