#include <fstream>
int main()
{
	unsigned i, n, phi[999999];
	unsigned long long x = 0;
	std::ifstream f("fractii.in");
	f >> n;
	f.close();
	for (i = 2; i <= n; phi[i++] = i - 2); 
	for (i = 2; i <= n; i++)
	for (unsigned j = 2 * i; j <= n;  j += i)phi[j] -= phi[i] ;
	for (i = 2; i <= n; i++)x+=phi[i]*2;
	std::ofstream g("fractii.out");
	g << x + 1;
	g.close();
}