#include<fstream>
#define maxn 1000000

using namespace std;

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

int n,phi[maxn];

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