-er bbb bbc bbd bbe bbk bbo bbr bbs bbt bcb bcc bcd bce bck bco bcr bcs bct bdb bdc bdd bde bdk bdo bdr bds bdt be- beb bec bed bee bek beo ber bes bet bkb bkc bke bkk bko bkr bks bkt bob boc bod boe bok boo bor bos bot brb brd bre brk bro brr brs brt bsb bsc bsd bse bsk bso bsr bss bst btb btc btd bte btk bto btr bts btt c-- cbb cbc cbd cbe cbk cbo cbr cbs cbt ccb ccc ccd cce cck cco ccr ccs cct cdb cdc cdd cde cdk cdo cdr cds cdt ce- ceb cec ced cee cek ceo cer ces cet ckb ckc ckd cko cks ckt co- cob coc cod coe cok coo cor cos cot crb crc crd cre crk cro crr crs crt csb csc csd cse csk cso csr css cst ctb ctc ctd cte ctk cto ctr cts ctt dbb dbc dbd dbe dbk dbo dbr dbs dbt dcb dcc dcd dce dck dco dcr dcs dct ddb ddc ddd dde ddk ddo ddr dds ddt de- deb dec ded dee dek deo der des det dkb dkc dke dkk dko dkr dks dkt dob doc dod doe dok doo dor dos dot drb drc drd dre drk dro drr drs drt dsb dsc dsd dse dsk dso dsr dss dst dtb dtc dtd dte dtk dto dtr dts dtt ebb ebc ebd ebe ebk ebo ebr ebs ebt ec- ecb ecc ecd ece eck eco ecr ecs ect ed- edb edc edd ede edk edo edr eds edt eeb eec eed eee eek eeo eer ees eet ekb ekc ekd eke eko ekr eks ekt eo- eob eoc eod eoe eok eoo eor eos eot erb erc erd ere erk ero err ers ert es- esb esc esd ese esk eso esr ess est etb etc etd ete etk eto etr ets ett k-t kbb kbc kbd kbe kbk kbo kbr kbs kcb kcc kcd kce kck kcr kcs kct kdb kdc kde kdk kdo kdr kds kdt ke- keb kec ked kee kek keo ker kes ket kkb kkc kke kkk kkr kks kkt kob koc kod koe kok koo kor kos kot krc krd krk kro krr krs krt ksb ksc ksd kse ksk kso ksr kss kst ktb ktc kte ktk kto ktr kts ktt ob- obb obc obd obe obk obo obr obs obt oc- ocb occ ocd ock oco ocr ocs oct odb odc odd ode odo odr ods odt oeb oec oed oee oeo oer oes oet okb okc okd oke okk oko okr oks oo- oob ooc ood ook ooo oor oos oot or- orb orc ord ore ork oro orr ors ort os- osb osc osd ose osk oso osr oss ost ot- otb otc otd ote otk oto otr ots ott rbb rbc rbd rbe rbk rbo rbr rbs rbt rcb rcc rcd rce rco rcr rcs rct rdb rdc rdd rde rdo rdr rds rdt re- reb rec red ree rek reo rer res ret rkb rkc rke rkk rko rks rkt rob roc rod roe rok roo ror ros rot rrb rrc rrd rrk rrr rrs rrt rsb rsc rsd rse rsk rso rsr rss rst rtb rtc rtd rte rtk rto rtr rts rtt sbb sbc sbd sbe sbk sbo sbr sbs sbt scb scc scd sce sck sco scr scs sct sdb sdc sdd sde sdk sdo sdr sds sdt se- seb sec sed see sek seo ser ses set sk- skb skc skd ske skk sko skr sks skt sob soc sod soe sok soo sor sos sot sr- srb src srd sre srk sro srr srs srt ss- ssb ssc ssd sse ssk sso ssr sss sst stb stc std ste stk sto str sts stt tbb tbc tbd tbe tbk tbo tbr tbs tbt tcb tcc tcd tce tck tco tcr tcs tct tdb tdc tdd tde tdk tdo tdr tds tdt te- teb tec ted tee tek teo ter tes tet tkb tkc tke tkk tko tkr tks tkt to- tob toc tod toe tok too tor tos tot trb trc trd tre trk tro trr trs trt tsb tsc tsd tse tsk tso tsr tss tst ttb ttc ttd tte ttk tto ttr tts ttt