a-a a-b aaa aab aad aao aav ab- aba abb abd abo abv ad- ada adb add ado adv aoa aob aod aoo aov av- ava avb avd avo baa bab bad bao bav bba bbb bbd bbo bda bdb bdd bdo bdv boa bob bod boo bov bva bvb bvd bvo bvv daa dab dad dao dav dba dbb dbd dbo dbv dda ddb ddd ddo doa dob dod doo dov dva dvb dvd oaa oab oad oao oav ob- oba obb obd obo obv oda odb odd odo odv oo- ooa oob ood ooo oov ov- ova ovb ovd ovo ovv v-a vaa vab vad vao vav vba vbd vbo vbv vdb vdd vdo vdv voa vob vod voo vov vva vvb vvo vvv