a-a a-b a-c aaa aab aac aag aan aao ab- aba abb abc abg abn abo ac- aca acb acc acg acn aco ag- aga agb agc agg agn ago an- ana anb anc ang ann ano aoa aob aoc aog aon aoo baa bab bac bag ban bao bba bbb bbc bbg bbn bbo bca bcb bcc bcg bcn bco bga bgb bgc bgg bgn bgo bna bnb bnc bng bnn bno boa bob boc bog bon boo c-- caa cab cac cag can cao cba cbb cbc cbg cbn cbo cca ccb ccc ccg ccn cco cga cgb cgc cgg cgn cgo cn- cna cnb cnc cng cnn cno co- coa cob coc cog con coo gaa gab gac gag gan gao gba gbc gbg gbn gbo gca gcb gcc gcg gcn gco gga ggb ggc ggg ggn ggo gna gnb gnc gnn gno goa gob goc gog gon goo naa nab nac nag nan nao nba nbb nbc nbg nbn nbo nca ncb ncc ncg ncn nco nga ngb ngc ngg ngn ngo nna nnb nnc nng nnn nno no- noa nob noc nog non noo oaa oab oac oag oan oao ob- oba obb obc obg obn obo oc- oca ocb occ ocg ocn oco oga ogc ogg ogn ogo on- ona onb onc ong onn ono oo- ooa oob ooc oog oon ooo