#include<iostream>
#include<fstream>
using namespace std;
int phi[2000000];
int main()
{
	fstream f("fractii.in",ios::in);
	fstream x("fractii.out",ios::out);
	long long n,g=0;
	f>>n;
	for (int i = 1; i <= n; ++i)
		phi[i] = i-1;
	for (int i = 2; i <= n; ++i)
		for (int j = 2*i; j <= n; j += i)
		  phi[j] -= phi[i];
	for(int i=2;i<=n;i++)
		g=g+phi[i]*2;
	x<<1+g;

}