#include<fstream>
#define N 1000001
using namespace std;
long long nr=0;
int n,i,j,v[N];
int main()
{
	ifstream f("fractii.in");
	ofstream g("fractii.out");
	f>>n;
	for (i=1; i<=n; i++)
		v[i]=i;
	for (i=2; i<=n; i++)
		if (v[i]==i)
			for (j=i; j<=n; j+=i)
			{
				v[j]/=i;
				v[j]*=(i-1);
			}
	for (i=1; i<=n; i++)
			nr+=v[i];
	nr=nr*2-1;
	g<<nr<<"\n";
	return 0;
}