#include <fstream>
using namespace std;

int main()
{
	ifstream fin("fractii.in");
	ofstream fout("fractii.out");
	unsigned long int n;
	fin >> n;
	unsigned long int fractii = n*n-n+1;
	for (unsigned long int i=2; i*i<=n; i++)
		for (unsigned long int j=i+i; j<=n; j=j+i)
			fractii = fractii - 2;
	fout << fractii;
	fin.close();
	fout.close();
	return 0;
}