a-a a-b a-c aaa aab aac aao aau aav ab- aba abb abc abo abu abv ac- aca acb acc aco acu acv aoa aob aoc aoo aou aov au- aua aub auc auo auv av- ava avb avc avo avu b-u baa bab bac bao bau bav bba bbb bbc bbo bbu bca bcb bcc bco bcu bcv boa bob boc boo bou bov bua bub buc buo buu bva bvb bvc bvo bvu bvv c-- caa cab cac cao cau cav cba cbb cbc cbo cbu cbv cca ccb ccc cco ccu ccv co- coa cob coc coo cou cov cua cub cuc cuo cuu cuv cva cvb cvc cvo cvu cvv oaa oab oac oao oau oav ob- oba obb obc obo obu obv oc- oca ocb occ oco ocu ocv oo- ooa oob ooc ooo oov ou- oua ouc ouo ov- ova ovb ovc ovo ovv ua- uaa uab uac uao uau uav uba ubb ubc ubo ubu ubv uca ucb ucc uco ucu ucv uoa uob uoc uoo uua uuc uuu uva uvb uvc uvo uvu uvv v-a vaa vab vac vao vau vav vba vbc vbo vbv vca vcc vco vcu voa vob voc voo vou vov vuv vva vvb vvc vvo vvv