a-a a-b a-c aaa aab aac aao aav ab- aba abb abc abo abv ac- aca acb acc aco acv aoa aob aoc aoo aov av- ava avb avc avo baa bab bac bao bav bba bbb bbc bbo bca bcb bcc bco bcv boa bob boc boo bov bva bvb bvc bvo bvv c-- caa cab cac cao cav cba cbb cbc cbo cbv cca ccb ccc cco ccv co- coa cob coc coo cov cva cvb cvc cvo cvv oaa oab oac oao oav ob- oba obb obc obo obv oc- oca ocb occ oco ocv oo- ooa oob ooc ooo oov ov- ova ovb ovc ovo ovv v-a vaa vab vac vao vav vba vbc vbo vbv vca vcc vco voa vob voc voo vov vva vvb vvc vvo vvv