PHP CodeIgniter class not found

I have the following classes

applicationControllersAppointments.php

applicationcontrollersapiv2AppointmentsV2.php

From AppointmentsV2 I want to access Appointments class, I tried many ways not working
I tried almost every thing always not working

require (APPPATH.'/Controllers/Appointments.php');

The class dose not use name scpace

class AppointmentsV2 extends EA_Controller {}
class Appointments extends EA_Controller {}
class EA_Controller extends CI_Controller {)

Error:

Message: Class ‘Appointments’ not found