#include <fstream>

using namespace std;

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

int n,p[1000001]={};
unsigned long long S;
int main()
{
	in>>n;
	for(int i=1;i<=n;i++)
		p[i]=1;
	for(int i=2;i<=n;i++)
	{
		p[i]=i-p[i];
		for(int j=2*i;j<=n;j+=i)
			p[j]++;
	}
	for(int i=2;i<=n;i++)
		S+=p[i];
	S*=2;
	S++;
	out<<S;
	return 0;
}