#include<fstream>
#define NrP 1000 
using namespace std;

long phi[1000000];
long s,n;
int i,j;

int main()
{	
	ifstream fin("fractii.in");
	ofstream fout("fractii.out");
	
	fin>>n;
	s = 1;

	for(i=2;i<=n;i++)
		phi[i] = i-1;
	
	for(i=2;i<=n;i++)
		for(j=2*i;j<=n;j+=i)
			phi[j] = phi[j] - phi[i];
		
for(i=2;i<=n;i++)
	s+=phi[i];

	fout<<2*s<<"\n";
	
return 0;
}