a-a a-b aaa aab aah aan aao ab- aba abb abh abn abo aha ahb ahh ahn aho an- ana anb anh ann ano aoa aob aoh aon aoo baa bab bah ban bao bba bbb bbh bbn bbo bha bhb bhh bho bna bnb bnn bno boa bob boh bon boo haa hab hah han hao hba hbb hbh hbn hbo hha hhb hhh hhn hho hna hnb hnh hnn hno hoa hob hoh hon hoo naa nab nah nan nao nba nbb nbn nbo nha nhb nhh nhn nna nnb nnh nnn nno no- noa nob noh non noo oaa oab oah oan oao ob- oba obb obh obn obo oha ohh ohn oho on- ona onb onh onn ono oo- ooa oob ooh oon ooo