a-a a-b a-c aaa aab aac aao aar aav ab- aba abb abc abo abr abv ac- aca acb acc aco acr acv aoa aob aoc aoo aor aov ar- ara arb arc aro arr arv av- ava avb avc avo avr baa bab bac bao bar bav bba bbb bbc bbo bbr bca bcb bcc bco bcr bcv boa bob boc boo bor bov bra brb bro brr brv bva bvb bvc bvo bvr bvv c-- caa cab cac cao car cav cba cbb cbc cbo cbr cbv cca ccb ccc cco ccr ccv co- coa cob coc coo cor cov cra crb crc cro crr crv cva cvb cvc cvo cvr cvv oaa oab oac oao oar oav ob- oba obb obc obo obr obv oc- oca ocb occ oco ocr ocv oo- ooa oob ooc ooo oor oov or- ora orb orc oro orr orv ov- ova ovb ovc ovo ovv ra- raa rab rac rao rar rav rba rbb rbc rbo rbr rca rcb rcc rco rcr rcv roa rob roc roo ror rov rra rrb rrc rrr rva rvb rvc rvo rvr rvv v-a vaa vab vac vao var vav vba vbc vbo vbr vbv vca vcc vco vcr voa vob voc voo vor vov vra vrb vrc vrr vva vvb vvc vvo vvr vvv