#include <iostream>
#include <fstream>

using namespace std;
int n;
int nr[1000001], k;
long long rasp;

void solve()
{
	for (int i = 2; i <= n; i++)
		nr[i] = i;
	for (int i = 2; i <= n; i++)
	{
		if (nr[i] == i)
		{
			for(int j = 2*i; j<=n; j+=i)
			{
				nr[j] /=nr[i];
				nr[j] *= nr[i]-1;
			}
			nr[i]--;
		}
		rasp += nr[i];
	}
}

int main()
{
	ifstream f("fractii.in");
	ofstream g("fractii.out");
	f >> n;
	solve();
	g << rasp*2+1;
	f.close();
	g.close();
	return 0;
}