#include <fstream>
std::ifstream cin("fractii.in");
std::ofstream cout("fractii.out");
#define maxn 1000000
int phi[maxn],n;
long long int sol=1;

int main()
{
	cin>>n;
	for(int i=1;i<=n;++i)
		phi[i]=i-1;
	for(int i=2;i<=n/2;++i)
		for(int j=2;i*j<=n;++j)
			phi[i*j]-=phi[i];
	for(int i=2;i<=n;++i)
		sol=sol + 2LL * phi[i];
	cout<<sol;
}