a-a a-b a-c aaa aab aac aar aau ab- aba abb abc abr abu ac- aca acb acc acr acu ar- ara arb arc arr aru au- aua aub auc aur b-u baa bab bac bar bau bba bbb bbc bbr bbu bca bcb bcc bcr bcu bra brb brr bru bua bub buc bur buu c-- caa cab cac car cau cba cbb cbc cbr cbu cca ccb ccc ccr ccu cra crb crc crr cru cua cub cuc cur cuu ra- raa rab rac rar rau rba rbb rbc rbr rbu rca rcb rcc rcr rcu rra rrb rrc rrr rru rua rub ruc rur ruu ua- uaa uab uac uar uau uba ubb ubc ubr ubu uca ucb ucc ucr ucu ur- ura urb urc urr uru uua uuc uur uuu