#include<fstream>
#define Nmax 1000002
using namespace std;
fstream f1,f2;
int n,i,j;
long long p[Nmax];
long long s;

int main()
{
	f1.open("fractii.in",ios::in);
	f2.open("fractii.out",ios::out);
	f1>>n;
	for(i=1;i<=n;++i)
		p[i]=i-1;
	s=0;
	for(i=2;i<=n;++i)
	{
		s+=p[i];
		for(j=i+i;j<=n;j+=i)
			p[j]-=p[i];
	}
	s=s*2+1;
	f2<<s;
	f1.close();
	f2.close();
	return 0;
}