a-a a-b aaa aab aad aaf aam aan ab- aba abb abd abf abm abn ad- ada adb add adf adm adn af- afa afb afd aff afm afn ama amb amd amf amm amn an- ana anb and anf anm ann baa bab bad baf bam ban bba bbb bbd bbf bbm bbn bda bdb bdd bdf bdm bfa bfb bfd bff bfm bfn bma bmb bmd bmf bmm bmn bna bnb bnd bnf bnn daa dab dad daf dam dan dba dbb dbd dbf dbm dbn dda ddb ddd ddf ddm ddn dfa dfb dfd dff dfm dfn dma dmb dmd dmf dmm dmn dna dnb dnd dnf dnm dnn faa fab fad faf fam fan fba fbb fbd fbf fbm fbn fda fdb fdd fdf fdm fdn ffa ffd fff ffm ffn fma fmb fmd fmf fmm fmn fna fnb fnd fnf fnm fnn m-f maa mab mad maf mam man mba mbb mbd mbf mbm mda mdb mdd mdf mdm mdn mfa mfb mfd mff mfm mfn mma mmb mmd mmf mmm mmn mna mnb mnf mnm mnn naa nab nad naf nam nan nba nbb nbd nbf nbm nbn nda ndb ndd ndf ndm ndn nfa nfb nfd nff nfn nma nmb nmd nmm nmn nna nnb nnf nnm nnn