sub t{(sprintf('%04b',@_)=~tr/01/ w/r)&'bcgw'}sub p{printf"%s%8s$/", t(15-$_),t$_ for@_;print$/}sub r{my($s,$h,%s)=@_;($s^15||p@$h)|r($_, [@$h,$_],$_,1,%s)for grep{!$s{$_}&&!($s&8&&~$s&$_&7)&&!(~$s&8&&$s&~ $_&7)&&($z=$s^$_)&8&&(($z&=7)<3|$z==4)}15,grep$_%3,1..14}r+0,[0],0,1