#include <fstream>

using namespace std;

#define N_MAX 1000001
#define FIN "fractii.in"
#define FOUT "fractii.out"
int phi[N_MAX],n;

int main()
{
	int k,i,j,s = 1;
	fstream 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;
	
	return 0;
}