#include <bits/stdc++.h>
using namespace std;

ifstream file_in("fractii.in");
ofstream file_out("fractii.out");

int i, j, n;
long long a[1000005];

void init()
{
	for (i = 2; i <= n; ++i)
		a[i] = i - 1;
}

void sum(long long& S)
{
	for (i = 2; i <= n; ++i)
	{
		S += a[i];
		for (j = i + i; j <= n; j += i)
			a[j] -= a[i];
	}
	S = S * 2 + 1;
}

int main()
{
	file_in >> n;
	init();

	long long S = 0;
	sum(S);

	file_out << S;
	return 0;
}