#include <fstream>
using namespace std;

long long n, S = 0, a[1000000], i;

int main()
{
	ifstream f("fractii.in");
	ofstream g("fractii.out");
	
	f >> n;
	
	for(i = 2; i <= n; ++i)
		a[i] = i - 1;
	
	for(i = 2; i <= n; ++i)
	{
		S = S + a[i];
		
		for(int j = 2; j * i <= n; ++j)
			a[j * i]--;
	}
	
	g << (2 * S) + 1;
	
	f.close();
	g.close();
	
	return 0;
}