#include<fstream>
using namespace std;
int n,phi[1000005];
long long sol;
int main()
{
	int i,j,lim;
	ifstream fin("fractii.in");
	fin>>n;
	fin.close();
	
	lim=n/2;
	for(i=1;i<=n;i++)
		phi[i]=i-1;
	for(i=1;i<=lim;i++)
		for(j=2*i;j<=n;j+=i)
			phi[j]-=phi[i];
	for(i=2;i<=n;i++)
		sol=sol+phi[i];
	sol=2*sol+1;
	
	ofstream fout("fractii.out");
	fout<<sol<<"\n";
	fout.close();
	return 0;
}