a-a a-b a-t aaa aab aan aar aat aau ab- aba abb abn abr abt abu an- ana anb ann anr ant anu ar- ara arb arn arr art aru at- ata atb atn atr att atu au- aua aub aun aur aut b-u baa bab ban bar bat bau bba bbb bbn bbr bbt bbu bna bnb bnn bnr bnt bnu bra brb brn brr brt bru bta btb btn btr btt btu bua bub bun bur but buu naa nab nan nar nat nau nba nbb nbn nbr nbt nbu nna nnb nnn nnt nnu nra nrb nrn nrr nrt nru nta ntb ntn ntr ntt ntu nua nub nun nur nut nuu ra- raa rab ran rar rat rau rba rbb rbn rbr rbt rbu rna rnb rnn rnr rnt rnu rra rrb rrn rrr rrt rru rta rtb rtn rtr rtt rtu rua rub run rur rut ruu taa tab tan tar tat tau tba tbb tbn tbr tbt tbu tna tnb tnn tnr tnt tra trb trn trr trt tru tta ttb ttn ttr ttt ttu tua tub tun tur tut tuu ua- uaa uab uan uar uat uau uba ubb ubn ubr ubt ubu un- una unb unn unr unt unu ur- ura urb urn urr urt uru uta utb utn utr utt utu uua uun uur uut uuu