-er bbb bbc bbe bbf bbk bbo bbr bbt bcb bcc bce bcf bck bco bcr bct be- beb bec bee bef bek beo ber bet bfb bfc bfe bff bfo bfr bft bkb bkc bke bkf bkk bko bkr bkt bob boc boe bof bok boo bor bot brb bre brf brk bro brr brt btb btc bte btf btk bto btr btt c-- cbb cbc cbe cbf cbk cbo cbr cbt ccb ccc cce ccf cck cco ccr cct ce- ceb cec cee cef cek ceo cer cet cfb cfc cfe cff cfk cfo cfr cft ckb ckc cko ckt co- cob coc coe cof cok coo cor cot crb crc cre crf crk cro crr crt ctb ctc cte ctf ctk cto ctr ctt ebb ebc ebe ebf ebk ebo ebr ebt ec- ecb ecc ece ecf eck eco ecr ect eeb eec eee eef eek eeo eer eet ef- efb efc efe eff efo efr eft ekb ekc eke ekf eko ekr ekt eo- eob eoc eoe eof eok eoo eor eot erb erc ere erf erk ero err ert etb etc ete etf etk eto etr ett fbb fbc fbe fbf fbk fbo fbr fbt fcb fcc fce fcf fck fco fcr fct feb fec fee fef fek feo fer fet ffc ffe fff ffk ffo ffr fft fkb fkc fkf fkk fkt fob foc foe fof fok foo for fot frb frc fre frf frk fro frr frt ftb ftc fte ftf ftk fto ftr ftt k-t kbb kbc kbe kbf kbk kbo kbr kcb kcc kce kck kcr kct ke- keb kec kee kef kek keo ker ket kfc kff kfo kkb kkc kke kkk kkr kkt kob koc koe kof kok koo kor kot krc krf krk kro krr krt ktb ktc kte ktf ktk kto ktr ktt ob- obb obc obe obf obk obo obr obt oc- ocb occ ocf ock oco ocr oct oeb oec oee oef oeo oer oet of- ofb ofc ofe off ofo ofr oft okb okc oke okk oko okr oo- oob ooc oof ook ooo oor oot or- orb orc ore orf ork oro orr ort ot- otb otc ote otf otk oto otr ott rbb rbc rbe rbf rbk rbo rbr rbt rcb rcc rce rcf rco rcr rct re- reb rec ree ref rek reo rer ret rfb rfc rfe rff rfk rfo rfr rft rkb rkc rke rkf rkk rko rkt rob roc roe rof rok roo ror rot rrb rrc rrf rrk rrr rrt rtb rtc rte rtf rtk rto rtr rtt tbb tbc tbe tbf tbk tbo tbr tbt tcb tcc tce tcf tck tco tcr tct te- teb tec tee tef tek teo ter tet tfb tfc tfe tff tfk tfo tfr tft tkb tkc tke tkk tko tkr tkt to- tob toc toe tof tok too tor tot trb trc tre trf trk tro trr trt ttb ttc tte ttf ttk tto ttr ttt