a-a a-b a-c a-t aaa aab aac aan aar aat aau ab- aba abb abc abn abr abt abu ac- aca acb acc acn acr act acu an- ana anb anc ann anr ant anu ar- ara arb arc arn arr art aru at- ata atb atc atn atr att atu au- aua aub auc aun aur aut b-u baa bab bac ban bar bat bau bba bbb bbc bbn bbr bbt bbu bca bcb bcc bcn bcr bct bcu bna bnb bnc bnn bnr bnt bnu bra brb brn brr brt bru bta btb btc btn btr btt btu bua bub buc bun bur but buu c-- caa cab cac can car cat cau cba cbb cbc cbn cbr cbt cbu cca ccb ccc ccn ccr cct ccu cn- cna cnb cnc cnn cnr cnt cnu cra crb crc crn crr crt cru cta ctb ctc ctn ctr ctt ctu cua cub cuc cun cur cut cuu naa nab nac nan nar nat nau nba nbb nbc nbn nbr nbt nbu nca ncb ncc ncn ncr nct ncu nna nnb nnc nnn nnt nnu nra nrb nrc nrn nrr nrt nru nta ntb ntc ntn ntr ntt ntu nua nub nuc nun nur nut nuu ra- raa rab rac ran rar rat rau rba rbb rbc rbn rbr rbt rbu rca rcb rcc rcn rcr rct rcu rna rnb rnc rnn rnr rnt rnu rra rrb rrc rrn rrr rrt rru rta rtb rtc rtn rtr rtt rtu rua rub ruc run rur rut ruu taa tab tac tan tar tat tau tba tbb tbc tbn tbr tbt tbu tca tcb tcc tcn tcr tct tcu tna tnb tnc tnn tnr tnt tra trb trc trn trr trt tru tta ttb ttc ttn ttr ttt ttu tua tub tuc tun tur tut tuu ua- uaa uab uac uan uar uat uau uba ubb ubc ubn ubr ubt ubu uca ucb ucc ucn ucr uct ucu un- una unb unc unn unr unt unu ur- ura urb urc urn urr urt uru uta utb utc utn utr utt utu uua uuc uun uur uut uuu