#include<fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int v[1000001],n;
void oiler()
{
	int i,j;
	for(i=2;i<=n;i++)
		v[i]=i;
	for(i=2;i<=n;i++)
		if(v[i]==i)
			for(j=i;j<=n;j=j+i)
				v[j]=v[j]/i*(i-1);
}
int main()
{
	int i;
	unsigned long long s=0;
	cin>>n;
	oiler();
	for(i=2;i<=n;i++)
		s=v[i]+s;
	s=s*2+1;
	cout<<s;
	return 0;
}