//Include
#include <fstream>
using namespace std;

//Definitii
#define ll long long int

//Constante
const int MAX_SIZE = (int)1e6+1;

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

int n;
int v[MAX_SIZE];
ll rasp;

//Main
int main()
{
	in >> n;
	for(int i=1 ; i<=n ; ++i)
		v[i] = i;
	
	for(int i=2 ; i<=n ; ++i)
		if(v[i] == i)
			for(int j=i ; j<=n ; j+=i)
				v[j] = (v[j] / i) * (i-1);
	
	for(int i=1 ; i<=n ; ++i)
		rasp += v[i];
	
	rasp *= 2;
	out << (rasp-1);
	
	in.close();
	out.close();
	return 0;
}