a-a a-b a-c aaa aab aac aar aau aav ab- aba abb abc abr abu abv ac- aca acb acc acr acu acv ar- ara arb arc arr aru arv au- aua aub auc aur auv av- ava avb avc avr avu b-u baa bab bac bar bau bav bba bbb bbc bbr bbu bca bcb bcc bcr bcu bcv bra brb brr bru brv bua bub buc bur buu bva bvb bvc bvr bvu bvv c-- caa cab cac car cau cav cba cbb cbc cbr cbu cbv cca ccb ccc ccr ccu ccv cra crb crc crr cru crv cua cub cuc cur cuu cuv cva cvb cvc cvr cvu cvv ra- raa rab rac rar rau rav rba rbb rbc rbr rbu rca rcb rcc rcr rcu rcv rra rrb rrc rrr rru rua rub ruc rur ruu ruv rva rvb rvc rvr rvu rvv ua- uaa uab uac uar uau uav uba ubb ubc ubr ubu ubv uca ucb ucc ucr ucu ucv ur- ura urb urc urr uru uua uuc uur uuu uva uvb uvc uvu uvv v-a vaa vab vac var vau vav vba vbc vbr vbv vca vcc vcr vcu vra vrb vrc vrr vru vur vuv vva vvb vvc vvr vvv