// Created by PhantomCracker. Copyright (c) PhantomCracker

#include <iostream>
#include <fstream>
#include <cmath>
using namespace std;

int ciurul_eratostene(int n)
{
	int nr = 0;
	int v[1000001];
	for(int i=2; i<=n; i++)
		v[i] = i-1;
	for(int i=2; i<=n; i++)
		for(int j=2*i; j<=n; j=j+i)
			v[j] = v[j] - v[i];
		for(int i=1; i<=n; i++)
			nr = nr + v[i];
		nr = nr*2;
		nr++;
		return nr;
}

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

	int n;

	f>>n;
	cout<<ciurul_eratostene(n);
	cout<<endl;
	return 0;
}