a-a a-b a-c a-t aaa aab aac aak aao aas aat ab- aba abb abc abk abo abs abt ac- aca acb acc ack aco acs act aka akb akc akk ako aks aoa aob aoc aok aoo aos aot as- asa asb asc ask aso ass ast at- ata atb atc ato ats att baa bab bac bak bao bas bat bba bbb bbc bbk bbo bbs bbt bca bcb bcc bck bco bcs bct bka bkb bkc bkk bko bks bkt boa bob boc bok boo bos bot bsa bsb bsc bsk bso bss bst bta btb btc btk bto bts btt c-- caa cab cac cak cao cas cat cba cbb cbc cbk cbo cbs cbt cca ccb ccc cck cco ccs cct cka ckb ckc cko cks ckt co- coa cob coc cok coo cos cot csa csb csc csk cso css cst cta ctb ctc ctk cto cts ctt k-t ka- kaa kab kac kak kao kas kat kba kbb kbc kbk kbo kbs kca kcb kcc kck kcs kct kkb kkc kkk kks kkt koa kob koc kok koo kos kot ksa ksb ksc ksk kso kss kst kta ktb ktc ktk kto kts ktt oaa oab oac oak oao oas oat ob- oba obb obc obk obo obs obt oc- oca ocb occ ock oco ocs oct oka okb okc okk oko oks oo- ooa oob ooc ook ooo oos oot os- osa osb osc osk oso oss ost ot- ota otb otc otk oto ots ott saa sab sac sak sao sas sat sba sbb sbc sbk sbo sbs sbt sca scb scc sck sco scs sct sk- ska skb skc skk sko sks skt soa sob soc sok soo sos sot ss- ssa ssb ssc ssk sso sss sst sta stb stc stk sto sts stt taa tab tac tak tao tas tat tba tbb tbc tbk tbo tbs tbt tca tcb tcc tck tco tcs tct tka tkb tkc tkk tko tks tkt to- toa tob toc tok too tos tot tsa tsb tsc tsk tso tss tst tta ttb ttc ttk tto tts ttt