a-a a-b aaa aab aad aae aaf aan ab- aba abb abd abe abf abn ad- ada adb add ade adf adn aea aeb aed aee aef aen af- afa afb afd afe aff afn an- ana anb and ane anf ann baa bab bad bae baf ban bba bbb bbd bbe bbf bbn bda bdb bdd bde bdf be- bea beb bed bee bef ben bfa bfb bfd bfe bff bfn bna bnb bnd bne bnf bnn daa dab dad dae daf dan dba dbb dbd dbe dbf dbn dda ddb ddd dde ddf ddn de- dea deb ded dee def den dfa dfb dfd dfe dff dfn dna dnb dnd dne dnf dnn eaa eab ead eae eaf ean eba ebb ebd ebe ebf ebn ed- eda edb edd ede edf edn eea eeb eed eee eef een ef- efa efb efd efe eff en- ena enb end ene enf enn faa fab fad fae faf fan fba fbb fbd fbe fbf fbn fda fdb fdd fde fdf fdn fea feb fed fee fef fen ffa ffd ffe fff ffn fna fnb fnd fne fnf fnn naa nab nad nae naf nan nba nbb nbd nbe nbf nbn nda ndb ndd nde ndf ndn ne- nea neb ned nee nef nen nfa nfb nfd nfe nff nfn nna nnb nne nnf nnn