-er a-a a-b a-c a-t aaa aab aac aae aak aao aar aas aat ab- aba abb abc abe abk abo abr abs abt ac- aca acb acc ace ack aco acr acs act aea aeb aec aee aek aeo aer aes aet aka akb akc ake akk ako akr aks aoa aob aoc aoe aok aoo aor aos aot ar- ara arb arc are ark aro arr ars art as- asa asb asc ase ask aso asr ass ast at- ata atb atc ate ato atr ats att baa bab bac bae bak bao bar bas bat bba bbb bbc bbe bbk bbo bbr bbs bbt bca bcb bcc bce bck bco bcr bcs bct be- bea beb bec bee bek beo ber bes bet bka bkb bkc bke bkk bko bkr bks bkt boa bob boc boe bok boo bor bos bot bra brb bre brk bro brr brs brt bsa bsb bsc bse bsk bso bsr bss bst bta btb btc bte btk bto btr bts btt c-- caa cab cac cae cak cao car cas cat cba cbb cbc cbe cbk cbo cbr cbs cbt cca ccb ccc cce cck cco ccr ccs cct ce- cea ceb cec cee cek ceo cer ces cet cka ckb ckc cko cks ckt co- coa cob coc coe cok coo cor cos cot cra crb crc cre crk cro crr crs crt csa csb csc cse csk cso csr css cst cta ctb ctc cte ctk cto ctr cts ctt eaa eab eac eae eak eao ear eas eat eba ebb ebc ebe ebk ebo ebr ebs ebt ec- eca ecb ecc ece eck eco ecr ecs ect eea eeb eec eee eek eeo eer ees eet eka ekb ekc eke eko ekr eks ekt eo- eoa eob eoc eoe eok eoo eor eos eot era erb erc ere erk ero err ers ert es- esa esb esc ese esk eso esr ess est eta etb etc ete etk eto etr ets ett k-t ka- kaa kab kac kae kak kao kar kas kat kba kbb kbc kbe kbk kbo kbr kbs kca kcb kcc kce kck kcr kcs kct ke- kea keb kec kee kek keo ker kes ket kkb kkc kke kkk kkr kks kkt koa kob koc koe kok koo kor kos kot kra krc krk kro krr krs krt ksa ksb ksc kse ksk kso ksr kss kst kta ktb ktc kte ktk kto ktr kts ktt oaa oab oac oae oak oao oar oas oat ob- oba obb obc obe obk obo obr obs obt oc- oca ocb occ ock oco ocr ocs oct oea oeb oec oee oeo oer oes oet oka okb okc oke okk oko okr oks oo- ooa oob ooc ook ooo oor oos oot or- ora orb orc ore ork oro orr ors ort os- osa osb osc ose osk oso osr oss ost ot- ota otb otc ote otk oto otr ots ott ra- raa rab rac rae rak rao rar ras rat rba rbb rbc rbe rbk rbo rbr rbs rbt rca rcb rcc rce rco rcr rcs rct re- rea reb rec ree rek reo rer res ret rkb rkc rke rkk rko rks rkt roa rob roc roe rok roo ror ros rot rra rrb rrc rrk rrr rrs rrt rsa rsb rsc rse rsk rso rsr rss rst rta rtb rtc rte rtk rto rtr rts rtt saa sab sac sae sak sao sar sas sat sba sbb sbc sbe sbk sbo sbr sbs sbt sca scb scc sce sck sco scr scs sct se- sea seb sec see sek seo ser ses set sk- ska skb skc ske skk sko skr sks skt soa sob soc soe sok soo sor sos sot sr- sra srb src sre srk sro srr srs srt ss- ssa ssb ssc sse ssk sso ssr sss sst sta stb stc ste stk sto str sts stt taa tab tac tae tak tao tar tas tat tba tbb tbc tbe tbk tbo tbr tbs tbt tca tcb tcc tce tck tco tcr tcs tct te- tea teb tec tee tek teo ter tes tet tka tkb tkc tke tkk tko tkr tks tkt to- toa tob toc toe tok too tor tos tot tra trb trc tre trk tro trr trs trt tsa tsb tsc tse tsk tso tsr tss tst tta ttb ttc tte ttk tto ttr tts ttt