<?php

class Point2D
{
	private $x;
	private $y;
	
	public function __construct($x, $y)
	{
		$this->x = x;
		$this->y = y;
	}
	
	public function getX()
	{
		return $this->x;
	}
	
	public function getY()
	{
		return $this->y;
	}
}

class Point3D extends Point2D
{
	private $z;
	
	public function __construct($x, $y, $z)
	{
		parent::__construct($x, $y);
		$this->z = $z;
	}
	
	public function getZ()
	{
		return $this->z;
	}
}