#include <fstream>
using namespace std;
int n,A[1000001],i;
long long rez;

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

void calc_phi()
{
	int i,j;
	// calcularea funtiei phi 
	// folosing ciurul lui Eratostene
	for (i=1;i<=n;++i)
		A[i]=i-1;
	for (i=2;i<=n;++i)
		for (j=2*i;j<=n;j+=i)
			A[j]-=A[i];
}

int main()
{
	f>>n;
	calc_phi();
	rez=1;
	for (i=1;i<=n;i++)
		rez+=2*A[i];
	g<<rez;
	f.close();
	g.close();
	return 0;
}