<?php
abstract class Tile
{
	abstract public function getWealthFactor(): int;
}
class Plains extends Tile
{
	private int $wealthfactor = 2;
	public function getWealthFactor(): int
	{
		return $this->wealthfactor;
	}
}
class DiamondPlains extends Plains
{
	public function getWealthFactor(): int
	{
		return parent::getWealthFactor() + 2;
	}
}