#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();
}