#include <fstream>
using namespace std;

#define N_MAX 1000001
#define FIN "fractii.in"
#define FOUT "fractii.out"

int phi[N_MAX];
int n;

int main()
{
	int k,i,j;
	long long s = 1;
	
	ifstream fin(FIN);
	ofstream fout(FOUT);

	fin >> n;
	
	//calculate phi function
	for(i = 1; i <= n; ++i)
		phi[i] = i-1;
	
	for(i = 2; i <= n; ++i)
		for(j = 2 * i; j <= n; j += i)
			phi[j] -= phi[i];
	
	for(k = 2; k <= n; ++k)
		s += 2*phi[k];
	
	fout << s << endl;

	return 0;
}