a-a a-b aaa aab aaf aam aao ab- aba abb abf abm abo af- afa afb aff afm afo ama amb amf amm amo aoa aob aof aom aoo baa bab baf bam bao bba bbb bbf bbm bbo bfa bfb bff bfm bfo bma bmb bmf bmm bmo boa bob bof bom boo faa fab faf fam fao fba fbb fbf fbm fbo ffa fff ffm ffo fma fmb fmf fmm fmo foa fob fof fom foo m-f m-o maa mab maf mam mao mba mbb mbf mbm mbo mfa mfb mff mfm mfo mma mmb mmf mmm mmo moa mob mof mom moo oaa oab oaf oam oao ob- oba obb obf obm obo of- ofa ofb off ofm ofo om- oma omb omf omm omo oo- ooa oob oof oom ooo