a-a a-b a-t aaa aab aaf aan aao aat ab- aba abb abf abn abo abt af- afa afb aff afn afo aft an- ana anb anf ann ano ant aoa aob aof aon aoo aot at- ata atb atf atn ato att baa bab baf ban bao bat bba bbb bbf bbn bbo bbt bfa bfb bff bfn bfo bft bna bnb bnf bnn bno bnt boa bob bof bon boo bot bta btb btf btn bto btt faa fab faf fan fao fat fba fbb fbf fbn fbo fbt ffa fff ffn ffo fft fna fnb fnf fnn fnt foa fob fof fon foo fot fta ftb ftf ftn fto ftt naa nab naf nan nao nat nba nbb nbf nbn nbo nbt nfa nfb nff nfn nfo nft nna nnb nnf nnn nno nnt no- noa nob nof non noo not nta ntb ntf ntn nto ntt oaa oab oaf oan oao oat ob- oba obb obf obn obo obt of- ofa ofb off ofn ofo oft on- ona onb onf onn ono ont oo- ooa oob oof oon ooo oot ot- ota otb otf otn oto ott taa tab taf tan tao tat tba tbb tbf tbn tbo tbt tfa tfb tff tfn tfo tft tna tnb tnf tnn tno tnt to- toa tob tof ton too tot tta ttb ttf ttn tto ttt