a-a a-b a-c a-t aaa aab aac aak aas aat ab- aba abb abc abk abs abt ac- aca acb acc ack acs act aka akb akc akk aks as- asa asb asc ask ass ast at- ata atb atc ats att baa bab bac bak bas bat bba bbb bbc bbk bbs bbt bca bcb bcc bck bcs bct bka bkb bkc bkk bks bkt bsa bsb bsc bsk bss bst bta btb btc btk bts btt c-- caa cab cac cak cas cat cba cbb cbc cbk cbs cbt cca ccb ccc cck ccs cct cka ckb ckc cks ckt csa csb csc csk css cst cta ctb ctc ctk cts ctt k-t ka- kaa kab kac kak kas kat kba kbb kbc kbk kbs kca kcb kcc kck kcs kct kkb kkc kkk kks kkt ksa ksb ksc ksk kss kst kta ktb ktc ktk kts ktt saa sab sac sak sas sat sba sbb sbc sbk sbs sbt sca scb scc sck scs sct sk- ska skb skc skk sks skt ss- ssa ssb ssc ssk sss sst sta stb stc stk sts stt taa tab tac tak tas tat tba tbb tbc tbk tbs tbt tca tcb tcc tck tcs tct tka tkb tkc tkk tks tkt tsa tsb tsc tsk tss tst tta ttb ttc ttk tts ttt