a-a a-b a-c a-t aaa aab aac aar aat aau ab- aba abb abc abr abt abu ac- aca acb acc acr act acu ar- ara arb arc arr art aru at- ata atb atc atr att atu au- aua aub auc aur aut b-u baa bab bac bar bat bau bba bbb bbc bbr bbt bbu bca bcb bcc bcr bct bcu bra brb brr brt bru bta btb btc btr btt btu bua bub buc bur but buu c-- caa cab cac car cat cau cba cbb cbc cbr cbt cbu cca ccb ccc ccr cct ccu cra crb crc crr crt cru cta ctb ctc ctr ctt ctu cua cub cuc cur cut cuu ra- raa rab rac rar rat rau rba rbb rbc rbr rbt rbu rca rcb rcc rcr rct rcu rra rrb rrc rrr rrt rru rta rtb rtc rtr rtt rtu rua rub ruc rur rut ruu taa tab tac tar tat tau tba tbb tbc tbr tbt tbu tca tcb tcc tcr tct tcu tra trb trc trr trt tru tta ttb ttc ttr ttt ttu tua tub tuc tur tut tuu ua- uaa uab uac uar uat uau uba ubb ubc ubr ubt ubu uca ucb ucc ucr uct ucu ur- ura urb urc urr urt uru uta utb utc utr utt utu uua uuc uur uut uuu