aaaa aaab aaap aaba aabb aabp aabt aaoo aapa aapo aapt aata aatt abaa abab abap abat abb- abba abbb abbo abbt aboa abob aboo abot abpa abpp abta aoba aopo apao apap apat apba apo- apoo apop apot appa appt apta aptt at-t ataa atab atap atat atob atop atot atta atto attp baaa baat baba babb babo bapa bapp bapt bata bato batt bbbb boab boat boba bobb bobo boob boop boot bopa bopp bota botb boto bott bpot btaa btbp btob bttb obba obbo obot ooaa ooba oooo ootb ootp opap opo- oppa oppo opto otap oto- otoo otpp otta otto paap paat paba pabt papa papb papp pata pato patt pbpa poat poba pobo poop poot pop- popa popo popp popt pota poto pott ppap ppoa pppa pppo pppp ppta pptt ptab ptop taa- taat taba tabb tabo taoa tapa tapo tapp tapt tata tatb tato tatt tbta tbtp toab toat toba tobo tobt tooa toot top- topa topo topp topt tota toto tott tpap tppa tppp tptp ttab ttbb ttop tttt