#include <fstream>
#include <numeric>

using namespace std;
const int NMAX = 1e6;
long long n, ans, phi[NMAX + 1];

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

void genPhi()
{
	int i, j;
	iota(phi, phi + NMAX + 1, 0);
	//
	for(i = 2; i <= NMAX; ++i)
		if(phi[i] == i)
			for(j = i; j <= NMAX; j += i)
				phi[j] = phi[j] / i * (i - 1);
}

int main()
{
	genPhi();
	f >> n;
	n++;
	while(n--)
		ans += phi[n] * 2;
	g << ans - 1;
	f.close();
	g.close();
	return 0;
}