#include<fstream>
using namespace std;
const int MAXN=1000002;
int n,phi[MAXN];
long long suma;
int main()
{
	ifstream fin("fractii.in");
	ofstream fout("fractii.out");

	fin>>n;
	int i,j;
	phi[1]=1;
	for (i=2;i<=n;++i)
		phi[i]=i-1;
	for (i=2;i<=n;++i)
	{
		suma=suma+phi[i];
		for (j=i+i;j<=n;j+=i)
			phi[j]-=phi[i];
	}
	fout<<suma*2+1<<'\n';

	fin.close();
	fout.close();
	return 0;
}