a-a a-b aaa aab aaf aah aan aao ab- aba abb abf abh abn abo af- afa afb aff afh afn afo aha ahb ahf ahh ahn aho an- ana anb anf anh ann ano aoa aob aof aoh aon aoo baa bab baf bah ban bao bba bbb bbf bbh bbn bbo bfa bfb bff bfh bfn bfo bha bhb bhf bhh bho bna bnb bnf bnn bno boa bob bof boh bon boo faa fab faf fah fan fao fba fbb fbf fbh fbn fbo ffa fff ffh ffn ffo fha fhb fhf fhh fhn fho fna fnb fnf fnh fnn foa fob fof foh fon foo haa hab haf hah han hao hba hbb hbf hbh hbn hbo hfa hfb hff hfh hfn hfo hha hhb hhf hhh hhn hho hna hnb hnf hnh hnn hno hoa hob hof hoh hon hoo naa nab naf nah nan nao nba nbb nbf nbn nbo nfa nfb nff nfn nfo nha nhb nhf nhh nhn nna nnb nnf nnh nnn nno no- noa nob nof noh non noo oaa oab oaf oah oan oao ob- oba obb obf obh obn obo of- ofa ofb off ofn ofo oha ohf ohh ohn oho on- ona onb onf onh onn ono oo- ooa oob oof ooh oon ooo