a-a a-b aaa aab aak aao aav aay ab- aba abb abk abo abv aby aka akb akk ako akv aoa aob aok aoo aov av- ava avb avk avo avy ay- aya ayk ayo baa bab bak bao bav bay bba bbb bbk bbo bby bka bkb bkk bko bkv boa bob bok boo bov boy bva bvb bvk bvo bvv by- bya byk byo ka- kaa kab kak kao kav kay kba kbb kbk kbo kkb kkk kkv kky koa kob kok koo koy kva kvb kvk kvo kvv kya kyo oaa oab oak oao oav ob- oba obb obk obo obv oby oka okb okk oko oo- ooa oob ook ooo oov ov- ova ovb ovo ovv oya oyo v-a vaa vab vak vao vav vay vba vbk vbo vbv vka vkb voa vob vok voo vov voy vva vvb vvo vvv yaa yab yak yao yav yay yby yka ykk yob yok yoo yoy yva yvo yvy yyb yyy