-er bbb bbc bbe bbk bbn bbo bbr bbs bbt bcb bcc bce bck bcn bco bcr bcs bct be- beb bec bee bek ben beo ber bes bet bkb bkc bke bkk bkn bko bkr bks bkt bnb bnc bne bnk bnn bno bnr bns bnt bob boc boe bok bon boo bor bos bot brb bre brk brn bro brr brs brt bsb bsc bse bsk bsn bso bsr bss bst btb btc bte btk btn bto btr bts btt c-- cbb cbc cbe cbk cbn cbo cbr cbs cbt ccb ccc cce cck ccn cco ccr ccs cct ce- ceb cec cee cek cen ceo cer ces cet ckb ckc cko cks ckt cn- cnb cnc cne cnn cno cnr cns cnt co- cob coc coe cok con coo cor cos cot crb crc cre crk crn cro crr crs crt csb csc cse csk csn cso csr css cst ctb ctc cte ctk ctn cto ctr cts ctt ebb ebc ebe ebk ebn ebo ebr ebs ebt ec- ecb ecc ece eck ecn eco ecr ecs ect eeb eec eee eek een eeo eer ees eet ekb ekc eke eko ekr eks ekt en- enb enc ene enk enn eno enr ens ent eo- eob eoc eoe eok eon eoo eor eos eot erb erc ere erk ern ero err ers ert es- esb esc ese esk esn eso esr ess est etb etc ete etk etn eto etr ets ett k-t kbb kbc kbe kbk kbn kbo kbr kbs kcb kcc kce kck kcn kcr kcs kct ke- keb kec kee kek ken keo ker kes ket kkb kkc kke kkk kkn kkr kks kkt kn- knc kne knk knn kno knr knt kob koc koe kok kon koo kor kos kot krc krk krn kro krr krs krt ksb ksc kse ksk ksn kso ksr kss kst ktb ktc kte ktk ktn kto ktr kts ktt nbb nbc nbe nbk nbn nbo nbr nbs nbt ncb ncc nce nck ncn nco ncr ncs nct ne- neb nec nee nek nen neo ner nes net nkc nke nkk nkn nko nkr nks nkt nnb nnc nne nnk nnn nno nns nnt no- nob noc noe nok non noo nor nos not nrb nrc nre nrk nrn nro nrr nrs nrt nsb nsc nse nsk nsn nso nsr nss nst ntb ntc nte ntk ntn nto ntr nts ntt ob- obb obc obe obk obn obo obr obs obt oc- ocb occ ock ocn oco ocr ocs oct oeb oec oee oen oeo oer oes oet okb okc oke okk oko okr oks on- onb onc one onk onn ono onr ons ont oo- oob ooc ook oon ooo oor oos oot or- orb orc ore ork orn oro orr ors ort os- osb osc ose osk osn oso osr oss ost ot- otb otc ote otk otn oto otr ots ott rbb rbc rbe rbk rbn rbo rbr rbs rbt rcb rcc rce rcn rco rcr rcs rct re- reb rec ree rek ren reo rer res ret rkb rkc rke rkk rko rks rkt rnb rnc rnn rno rnr rns rnt rob roc roe rok ron roo ror ros rot rrb rrc rrk rrn rrr rrs rrt rsb rsc rse rsk rsn rso rsr rss rst rtb rtc rte rtk rtn rto rtr rts rtt sbb sbc sbe sbk sbn sbo sbr sbs sbt scb scc sce sck scn sco scr scs sct se- seb sec see sek sen seo ser ses set sk- skb skc ske skk sko skr sks skt snb snc sne snk snn sno snr sns snt sob soc soe sok son soo sor sos sot sr- srb src sre srk srn sro srr srs srt ss- ssb ssc sse ssk ssn sso ssr sss sst stb stc ste stk stn sto str sts stt tbb tbc tbe tbk tbn tbo tbr tbs tbt tcb tcc tce tck tcn tco tcr tcs tct te- teb tec tee tek ten teo ter tes tet tkb tkc tke tkk tko tkr tks tkt tnb tnc tne tnk tnn tno tnr tns tnt to- tob toc toe tok ton too tor tos tot trb trc tre trk trn tro trr trs trt tsb tsc tse tsk tsn tso tsr tss tst ttb ttc tte ttk ttn tto ttr tts ttt