// Craciun Catalin
//  Infoarena
//   Fractii

#include <fstream>

#define NMax 1000005

using namespace std;

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

int n; long long rez = 0;
int A[NMax];

void solve() {

	for (int i=1;i<=n;i++) A[i] = i-1;
	for (int i=2;i<=n;i++)
		for (int j=i+i;j<=n;j+=i)
			A[j] -= A[i];

	for (int i=2;i<=n;i++)
		rez += A[i];

	rez *= 2;
	rez++;
}

int main() {

	f>>n;	
	f.close();

	solve();

	g<<rez<<'\n';
	g.close();

	return 0;
}