a-be aaaa aaab aaae aaba aabb aabt aaea aata aatt abaa abab abae abat abb- abba abbb abbe abbt abee abet abta aeta aett at-t ataa atab atae atat atea atee atta atte baaa baat baba babb babe bata bate batt bbbb bbeb bbet beat beba bebb bebe beeb beet beta bete bett btaa bttb eaba eata eate ebba eeea eeee eeta eete etat etee etta ette taa- taat taba tabb tabe tata tatb tate tatt tbta teat teba teet teta tete tett ttab ttbb tttt