-er a-a a-b a-c a-t aaa aab aac aae aak aar aas aat ab- aba abb abc abe abk abr abs abt ac- aca acb acc ace ack acr acs act aea aeb aec aee aek aer aes aet aka akb akc ake akk akr aks ar- ara arb arc are ark arr ars art as- asa asb asc ase ask asr ass ast at- ata atb atc ate atr ats att baa bab bac bae bak bar bas bat bba bbb bbc bbe bbk bbr bbs bbt bca bcb bcc bce bck bcr bcs bct be- bea beb bec bee bek ber bes bet bka bkb bkc bke bkk bkr bks bkt bra brb bre brk brr brs brt bsa bsb bsc bse bsk bsr bss bst bta btb btc bte btk btr bts btt c-- caa cab cac cae cak car cas cat cba cbb cbc cbe cbk cbr cbs cbt cca ccb ccc cce cck ccr ccs cct ce- cea ceb cec cee cek cer ces cet cka ckb ckc cks ckt cra crb crc cre crk crr crs crt csa csb csc cse csk csr css cst cta ctb ctc cte ctk ctr cts ctt eaa eab eac eae eak ear eas eat eba ebb ebc ebe ebk ebr ebs ebt ec- eca ecb ecc ece eck ecr ecs ect eea eeb eec eee eek eer ees eet eka ekb ekc eke ekr eks ekt era erb erc ere erk err ers ert es- esa esb esc ese esk esr ess est eta etb etc ete etk etr ets ett k-t ka- kaa kab kac kae kak kar kas kat kba kbb kbc kbe kbk kbr kbs kca kcb kcc kce kck kcr kcs kct ke- kea keb kec kee kek ker kes ket kkb kkc kke kkk kkr kks kkt kra krc krk krr krs krt ksa ksb ksc kse ksk ksr kss kst kta ktb ktc kte ktk ktr kts ktt ra- raa rab rac rae rak rar ras rat rba rbb rbc rbe rbk rbr rbs rbt rca rcb rcc rce rcr rcs rct re- rea reb rec ree rek rer res ret rkb rkc rke rkk rks rkt rra rrb rrc rrk rrr rrs rrt rsa rsb rsc rse rsk rsr rss rst rta rtb rtc rte rtk rtr rts rtt saa sab sac sae sak sar sas sat sba sbb sbc sbe sbk sbr sbs sbt sca scb scc sce sck scr scs sct se- sea seb sec see sek ser ses set sk- ska skb skc ske skk skr sks skt sr- sra srb src sre srk srr srs srt ss- ssa ssb ssc sse ssk ssr sss sst sta stb stc ste stk str sts stt taa tab tac tae tak tar tas tat tba tbb tbc tbe tbk tbr tbs tbt tca tcb tcc tce tck tcr tcs tct te- tea teb tec tee tek ter tes tet tka tkb tkc tke tkk tkr tks tkt tra trb trc tre trk trr trs trt tsa tsb tsc tse tsk tsr tss tst tta ttb ttc tte ttk ttr tts ttt