a-a a-b a-c a-t aaa aab aac aak aao aat ab- aba abb abc abk abo abt ac- aca acb acc ack aco act aka akb akc akk ako aoa aob aoc aok aoo aot at- ata atb atc ato att baa bab bac bak bao bat bba bbb bbc bbk bbo bbt bca bcb bcc bck bco bct bka bkb bkc bkk bko bkt boa bob boc bok boo bot bta btb btc btk bto btt c-- caa cab cac cak cao cat cba cbb cbc cbk cbo cbt cca ccb ccc cck cco cct cka ckb ckc cko ckt co- coa cob coc cok coo cot cta ctb ctc ctk cto ctt k-t ka- kaa kab kac kak kao kat kba kbb kbc kbk kbo kca kcb kcc kck kct kkb kkc kkk kkt koa kob koc kok koo kot kta ktb ktc ktk kto ktt oaa oab oac oak oao oat ob- oba obb obc obk obo obt oc- oca ocb occ ock oco oct oka okb okc okk oko oo- ooa oob ooc ook ooo oot ot- ota otb otc otk oto ott taa tab tac tak tao tat tba tbb tbc tbk tbo tbt tca tcb tcc tck tco tct tka tkb tkc tkk tko tkt to- toa tob toc tok too tot tta ttb ttc ttk tto ttt