#include <fstream>

using namespace std;

bool prim(int x)
{
	for(int d = 2; d <= x/2; d++)
		if(!(x%d))
			return 0;
	return 1;
}

int main()
{
	ifstream in("fractii.in");
	ofstream out("fractii.out");

	int n, sum = 0;

	in >> n;
	
	for(int d = 2; d <= n/2; d++)
	{
		if(prim(d))
		{
			sum += (n/d)*((n/d)-1)/2;
			// out << d  << " " << (n/d)*((n/d)-1)/2 << endl;
		}
	}

	out << n*(n-1)-(2*sum)+1;

}