a-a a-b a-c aaa aab aac aak aar aau ab- aba abb abc abk abr abu ac- aca acb acc ack acr acu aka akb akc akk akr aku ar- ara arb arc ark arr aru au- aua aub auc auk aur b-u baa bab bac bak bar bau bba bbb bbc bbk bbr bbu bca bcb bcc bck bcr bcu bka bkb bkc bkk bkr bra brb brk brr bru bua bub buc buk bur buu c-- caa cab cac cak car cau cba cbb cbc cbk cbr cbu cca ccb ccc cck ccr ccu cka ckb ckc cra crb crc crk crr cru cua cub cuc cuk cur cuu ka- kaa kab kac kak kar kau kba kbb kbc kbk kbr kbu kca kcb kcc kck kcr kcu kkb kkc kkk kkr kku kra krc krk krr kru kub kuc kuk kur kuu ra- raa rab rac rak rar rau rba rbb rbc rbk rbr rbu rca rcb rcc rcr rcu rkb rkc rkk rku rra rrb rrc rrk rrr rru rua rub ruc ruk rur ruu ua- uaa uab uac uak uar uau uba ubb ubc ubk ubr ubu uca ucb ucc uck ucr ucu uka ukb ukc ukk ukr uku ur- ura urb urc urk urr uru uua uuc uur uuu