a-a a-b a-c aaa aab aac aan aao aar aau ab- aba abb abc abn abo abr abu ac- aca acb acc acn aco acr acu an- ana anb anc ann ano anr anu aoa aob aoc aon aoo aor aou ar- ara arb arc arn aro arr aru au- aua aub auc aun auo aur b-u baa bab bac ban bao bar bau bba bbb bbc bbn bbo bbr bbu bca bcb bcc bcn bco bcr bcu bna bnb bnc bnn bno bnr bnu boa bob boc bon boo bor bou bra brb brn bro brr bru bua bub buc bun buo bur buu c-- caa cab cac can cao car cau cba cbb cbc cbn cbo cbr cbu cca ccb ccc ccn cco ccr ccu cn- cna cnb cnc cnn cno cnr cnu co- coa cob coc con coo cor cou cra crb crc crn cro crr cru cua cub cuc cun cuo cur cuu naa nab nac nan nao nar nau nba nbb nbc nbn nbo nbr nbu nca ncb ncc ncn nco ncr ncu nna nnb nnc nnn nno nnu no- noa nob noc non noo nor nou nra nrb nrc nrn nro nrr nru nua nub nuc nun nuo nur nuu oaa oab oac oan oao oar oau ob- oba obb obc obn obo obr obu oc- oca ocb occ ocn oco ocr ocu on- ona onb onc onn ono onr onu oo- ooa oob ooc oon ooo oor or- ora orb orc orn oro orr oru ou- oua ouc oun ouo our ra- raa rab rac ran rao rar rau rba rbb rbc rbn rbo rbr rbu rca rcb rcc rcn rco rcr rcu rna rnb rnc rnn rno rnr rnu roa rob roc ron roo ror rou rra rrb rrc rrn rrr rru rua rub ruc run ruo rur ruu ua- uaa uab uac uan uao uar uau uba ubb ubc ubn ubo ubr ubu uca ucb ucc ucn uco ucr ucu un- una unb unc unn uno unr unu uoa uob uoc uon uoo uor ur- ura urb urc urn uro urr uru uua uuc uun uur uuu