Charlie is green. Charlie is white. Dave is red. Dave is young. Fiona is blue. Fiona is young. Gary is red. All round things are green. If something is green then it is young. If something is round and green then it is white. If something is green and not red then it is smart. If something is red and not blue then it is smart. If something is red and round then it is green. If Gary is white then Gary is round. Smart things are white. If something is green then it is smart.
Gary is not green.