a-a a-b a-c a-t aaa aab aac aaf aak aao aat ab- aba abb abc abf abk abo abt ac- aca acb acc acf ack aco act af- afa afb afc aff afk afo aft aka akb akc akk ako aoa aob aoc aof aok aoo aot at- ata atb atc atf ato att baa bab bac baf bak bao bat bba bbb bbc bbf bbk bbo bbt bca bcb bcc bcf bck bco bct bfa bfb bfc bff bfo bft bka bkb bkc bkf bkk bko bkt boa bob boc bof bok boo bot bta btb btc btf btk bto btt c-- caa cab cac caf cak cao cat cba cbb cbc cbf cbk cbo cbt cca ccb ccc ccf cck cco cct cfa cfb cfc cff cfk cfo cft cka ckb ckc cko ckt co- coa cob coc cof cok coo cot cta ctb ctc ctf ctk cto ctt faa fab fac faf fak fao fat fba fbb fbc fbf fbk fbo fbt fca fcb fcc fcf fck fco fct ffa ffc fff ffk ffo fft fka fkb fkc fkf fkk fkt foa fob foc fof fok foo fot fta ftb ftc ftf ftk fto ftt k-t ka- kaa kab kac kaf kak kao kat kba kbb kbc kbf kbk kbo kca kcb kcc kck kct kfa kfc kff kfo kkb kkc kkk kkt koa kob koc kof kok koo kot kta ktb ktc ktf ktk kto ktt oaa oab oac oaf oak oao oat ob- oba obb obc obf obk obo obt oc- oca ocb occ ocf ock oco oct of- ofa ofb ofc off ofo oft oka okb okc okk oko oo- ooa oob ooc oof ook ooo oot ot- ota otb otc otf otk oto ott taa tab tac taf tak tao tat tba tbb tbc tbf tbk tbo tbt tca tcb tcc tcf tck tco tct tfa tfb tfc tff tfk tfo tft tka tkb tkc tkk tko tkt to- toa tob toc tof tok too tot tta ttb ttc ttf ttk tto ttt