#include <iostream>
#include <fstream>
#include <set>
#include <vector>
#include <list>
#include <queue>
#include <algorithm>

//merci pauldb de solutie :)

using namespace std;

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

int phi[1000001];

int main()
{
	int i, j, nr = 1;
	f >> n;
	for (i = 1; i <= n; i++) phi[i] = i;

	for (i = 2; i <= n; i++)
		if (phi[i] == i)
			for (j = i; j <= n; j += i) phi[j] = phi[j] / i * (i - 1);

	for (i = 2; i <= n; i++)
		nr += 2 * phi[i];

	g << nr;

	return 0;
}