a-a a-b a-c aaa aab aac aak aan aar aau ab- aba abb abc abk abn abr abu ac- aca acb acc ack acn acr acu aka akb akc akk akn akr aku an- ana anb anc ank ann anr anu ar- ara arb arc ark arn arr aru au- aua aub auc auk aun aur b-u baa bab bac bak ban bar bau bba bbb bbc bbk bbn bbr bbu bca bcb bcc bck bcn bcr bcu bka bkb bkc bkk bkn bkr bna bnb bnc bnk bnn bnr bnu bra brb brk brn brr bru bua bub buc buk bun bur buu c-- caa cab cac cak can car cau cba cbb cbc cbk cbn cbr cbu cca ccb ccc cck ccn ccr ccu cka ckb ckc cn- cna cnb cnc cnn cnr cnu cra crb crc crk crn crr cru cua cub cuc cuk cun cur cuu ka- kaa kab kac kak kan kar kau kba kbb kbc kbk kbn kbr kbu kca kcb kcc kck kcn kcr kcu kkb kkc kkk kkn kkr kku kn- kna knc knk knn knr knu kra krc krk krn krr kru kub kuc kuk kun kur kuu naa nab nac nak nan nar nau nba nbb nbc nbk nbn nbr nbu nca ncb ncc nck ncn ncr ncu nka nkc nkk nkn nkr nku nna nnb nnc nnk nnn nnu nra nrb nrc nrk nrn nrr nru nua nub nuc nuk nun nur nuu ra- raa rab rac rak ran rar rau rba rbb rbc rbk rbn rbr rbu rca rcb rcc rcn rcr rcu rkb rkc rkk rku rna rnb rnc rnn rnr rnu rra rrb rrc rrk rrn rrr rru rua rub ruc ruk run rur ruu ua- uaa uab uac uak uan uar uau uba ubb ubc ubk ubn ubr ubu uca ucb ucc uck ucn ucr ucu uka ukb ukc ukk ukn ukr uku un- una unb unc unk unn unr unu ur- ura urb urc urk urn urr uru uua uuc uun uur uuu