a-a a-b a-c aaa aab aac aan aar aau ab- aba abb abc abn abr abu ac- aca acb acc acn acr acu an- ana anb anc ann anr anu ar- ara arb arc arn arr aru au- aua aub auc aun aur b-u baa bab bac ban bar bau bba bbb bbc bbn bbr bbu bca bcb bcc bcn bcr bcu bna bnb bnc bnn bnr bnu bra brb brn brr bru bua bub buc bun bur buu c-- caa cab cac can car cau cba cbb cbc cbn cbr cbu cca ccb ccc ccn ccr ccu cn- cna cnb cnc cnn cnr cnu cra crb crc crn crr cru cua cub cuc cun cur cuu naa nab nac nan nar nau nba nbb nbc nbn nbr nbu nca ncb ncc ncn ncr ncu nna nnb nnc nnn nnu nra nrb nrc nrn nrr nru nua nub nuc nun nur nuu ra- raa rab rac ran rar rau rba rbb rbc rbn rbr rbu rca rcb rcc rcn rcr rcu rna rnb rnc rnn rnr rnu rra rrb rrc rrn rrr rru rua rub ruc run rur ruu ua- uaa uab uac uan uar uau uba ubb ubc ubn ubr ubu uca ucb ucc ucn ucr ucu un- una unb unc unn unr unu ur- ura urb urc urn urr uru uua uuc uun uur uuu