#include <fstream>
#include <cmath>
#include <iostream>
long int x[1000001];
using namespace std;

int main()
{
	long int i, n, q;
	long long l = 1;


	ifstream a("fractii.in");
	ofstream b("fractii.out");
	a >> n;
	a.close();
	for (i = 1; i <= n; i++) 
	{
		x[i] = i - 1; 
	} 
	for (i = 2; i <= n; i++) 
	{ 
		for (q = 2 * i; q <= n; q = q + i)x[q] = x[q] - x[i]; 
	}
	for (i = 1; i <= n; i++) 
		l = l + 2 * x[i];


	b << l;
	b.close();
	return 0;
}