concat.while

//Candidate Number: 249763
(* concat.while
*)

concat read X {
	Z := nil;
	Y := nil;
	while X {
		listOfLists := hd X;
		X := tl X;
		while listOfLists {
			currentItem := hd listOfLists;
			listOfLists := tl listOfLists;
			Z := cons currentItem Z
		}

	};
	while Z {
		currentItem := hd Z;
		Z := tl Z;
		Y := cons currentItem Y
	}

}
write Y