#include<fstream.h>

long long phi[1000001], n;
void calc()
{
	long i, j;
	for (i=1; i<=n; i++) phi[i]=i;

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