a-a a-b aaa aab aaf aam aan aao ab- aba abb abf abm abn abo af- afa afb aff afm afn afo ama amb amf amm amn amo an- ana anb anf anm ann ano aoa aob aof aom aon aoo baa bab baf bam ban bao bba bbb bbf bbm bbn bbo bfa bfb bff bfm bfn bfo bma bmb bmf bmm bmn bmo bna bnb bnf bnn bno boa bob bof bom bon boo faa fab faf fam fan fao fba fbb fbf fbm fbn fbo ffa fff ffm ffn ffo fma fmb fmf fmm fmn fmo fna fnb fnf fnm fnn foa fob fof fom fon foo m-f m-o maa mab maf mam man mao mba mbb mbf mbm mbo mfa mfb mff mfm mfn mfo mma mmb mmf mmm mmn mmo mna mnb mnf mnm mnn mno moa mob mof mom mon moo naa nab naf nam nan nao nba nbb nbf nbm nbn nbo nfa nfb nff nfn nfo nma nmb nmm nmn nmo nna nnb nnf nnm nnn nno no- noa nob nof nom non noo oaa oab oaf oam oan oao ob- oba obb obf obm obn obo of- ofa ofb off ofm ofn ofo om- oma omb omf omm omn omo on- ona onb onf onn ono oo- ooa oob oof oom oon ooo