a-a a-b aaa aab aag aan aao ab- aba abb abg abn abo ag- aga agb agg agn ago an- ana anb ang ann ano aoa aob aog aon aoo baa bab bag ban bao bba bbb bbg bbn bbo bga bgb bgg bgn bgo bna bnb bng bnn bno boa bob bog bon boo gaa gab gag gan gao gba gbg gbn gbo gga ggb ggg ggn ggo gna gnb gnn gno goa gob gog gon goo naa nab nag nan nao nba nbb nbg nbn nbo nga ngb ngg ngn ngo nna nnb nng nnn nno no- noa nob nog non noo oaa oab oag oan oao ob- oba obb obg obn obo oga ogg ogn ogo on- ona onb ong onn ono oo- ooa oob oog oon ooo