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