import java.util.ArrayList;

public class ChemicalMachine $\{$

public void add$($String chemical$)\{$

throw new UnsupportedOperationException$("$Waiting to be implemented."$)$;

$\}$

public void applyHeat$()\{$

throw new UnsupportedOperationException$("$Waiting to be implemented."$)$;

$\}$

public ArrayList emptyMachine$()\{$

throw new UnsupportedOperationException$("$Waiting to be implemented."$)$;

$\}$

public static void main$($String$[]$ args$)\{$

ChemicalMachine machine $=$ new ChemicalMachine$()$;

machine.add$("$GREEN$")$;

machine.add$("$YELLOW$")$;

machine.applyHeat$()$;

System.out.println$($String$.$join$(",",$ machine.emptyMachine$()))$; $//$ should print BROWN

machine.add$("$RED$")$;

machine.add$("$YELLOW$")$;

machine.applyHeat$()$;

System.out.println$($String$.$join$(",",$ machine.emptyMachine$()))$; $//$ should print UNKNOWN

$\}$

$\}$