#include<fstream>
using namespace std;
unsigned viz[1000001];
int main ()
{
	ifstream f("fractii.in");
	ofstream g("fractii.out");
	unsigned n,i,k;
	long int s=0;
	f>>n;
	unsigned a[n+1];
	for(i=2;i<=n;i++) a[i]=i;
	for(i=2;i<=n;i++)
		if(!viz[i])
		{
			a[i]--;
			k=2;
			while(k*i<=n)
			{
				viz[k*i]=1;
				a[k*i]-=a[k*i]/i;
				k++;
			}
		}
	for(i=2;i<=n;i++) s+=2*a[i];
	g<<s+1;
	f.close();g.close();
	return 0;
}