a-a a-b aaa aab aaf aan aau ab- aba abb abf abn abu af- afa afb aff afn afu an- ana anb anf ann anu au- aua aub auf aun b-u baa bab baf ban bau bba bbb bbf bbn bbu bfa bfb bff bfn bfu bna bnb bnf bnn bnu bua bub buf bun buu faa fab faf fan fau fba fbb fbf fbn fbu ffa fff ffn ffu fna fnb fnf fnn fnu fua fub fuf fun fuu naa nab naf nan nau nba nbb nbf nbn nbu nfa nfb nff nfn nfu nna nnb nnf nnn nnu nua nub nun nuu ua- uaa uab uaf uan uau uba ubb ubf ubn ubu ufa uff ufn ufu un- una unb unf unn unu uua uun uuu