#include<fstream>
#define maxn 1000000

using namespace std;

ifstream in("fractii.in");
ofstream out("fractii.out");

int n,phi[maxn];

int sum()
{
	int suma=0;
	for(int i=1;i<=n;i++)
		suma=suma+phi[i];
	return suma;
}

int main()
{
	in>>n;
	int rasp=2*n-1;
	for (int i=1;i<=n;i++) phi[i]=i;
	for (int i=2;i<=n;i++)
		   if (phi[i]==i)
			  for (int j=i;j<=n;j+=i) phi[j] /=i, phi[j] *= (i-1);
	out<<rasp+sum()<<"\n";
	return 0;
}