#include <fstream>
using namespace std;

int main (void)
{
	ifstream in("fractii.in");
	ofstream out("fractii.out");
	int i,j,n,count=0,phi[1000000];
	in>>n;
	in.close();
	for (int i=1;i<=n;i++) 
		phi[i]=i;
	for (int i=2;i<=n;i++)
		if (phi[i]==i)
			for (j=i;j<=n;j+=i) 
				phi[j] /=i, phi[j] *= (i-1);
	for (i=1;i<=n;i++)
		count=count+phi[i];
	out<<2*count-1;
	out.close();
	return 0;
}