#include<fstream>
#define maxn 1000001

using namespace std;

ifstream in("fractii.in");
ofstream out("fractii.out");

int n,phi[maxn];

int main()
{
	in>>n;
	long long rasp,i,j;
	for(i=1;i<=n;++i)
	phi[i]=i;
	rasp=0;	
	for(i=2;i<=n;i++)
	{
		if(phi[i]==i)
		for(j=i;j<=n;j+=i)
		{
			phi[j]=phi[j]/i;
			phi[j]=phi[j]*(i-1);
		}		
	}
	for(int i=1;i<=n;i++)
		rasp+=phi[i];
	rasp=2*rasp-1;
	out<<rasp<<"\n";
	return 0;
}