-er bbb bbc bbe bbf bbk bbn bbo bbr bcb bcc bce bcf bck bcn bco bcr be- beb bec bee bef bek ben beo ber bfb bfc bfe bff bfn bfo bfr bkb bkc bke bkf bkk bkn bko bkr bnb bnc bne bnf bnk bnn bno bnr bob boc boe bof bok bon boo bor brb bre brf brk brn bro brr c-- cbb cbc cbe cbf cbk cbn cbo cbr ccb ccc cce ccf cck ccn cco ccr ce- ceb cec cee cef cek cen ceo cer cfb cfc cfe cff cfk cfn cfo cfr ckb ckc cko cn- cnb cnc cne cnf cnn cno cnr co- cob coc coe cof cok con coo cor crb crc cre crf crk crn cro crr ebb ebc ebe ebf ebk ebn ebo ebr ec- ecb ecc ece ecf eck ecn eco ecr eeb eec eee eef eek een eeo eer ef- efb efc efe eff efo efr ekb ekc eke ekf eko ekr en- enb enc ene enf enk enn eno enr eo- eob eoc eoe eof eok eon eoo eor erb erc ere erf erk ern ero err fbb fbc fbe fbf fbk fbn fbo fbr fcb fcc fce fcf fck fcn fco fcr feb fec fee fef fek fen feo fer ffc ffe fff ffk ffn ffo ffr fkb fkc fkf fkk fnb fnc fne fnf fnk fnn fnr fob foc foe fof fok fon foo for frb frc fre frf frk frn fro frr kbb kbc kbe kbf kbk kbn kbo kbr kcb kcc kce kck kcn kcr ke- keb kec kee kef kek ken keo ker kfc kff kfo kkb kkc kke kkk kkn kkr kn- knc kne knf knk knn kno knr kob koc koe kof kok kon koo kor krc krf krk krn kro krr nbb nbc nbe nbf nbk nbn nbo nbr ncb ncc nce ncf nck ncn nco ncr ne- neb nec nee nef nek nen neo ner nfb nfc nfe nff nfk nfn nfo nfr nkc nke nkf nkk nkn nko nkr nnb nnc nne nnf nnk nnn nno no- nob noc noe nof nok non noo nor nrb nrc nre nrf nrk nrn nro nrr ob- obb obc obe obf obk obn obo obr oc- ocb occ ocf ock ocn oco ocr oeb oec oee oef oen oeo oer of- ofb ofc ofe off ofn ofo ofr okb okc oke okk oko okr on- onb onc one onf onk onn ono onr oo- oob ooc oof ook oon ooo oor or- orb orc ore orf ork orn oro orr rbb rbc rbe rbf rbk rbn rbo rbr rcb rcc rce rcf rcn rco rcr re- reb rec ree ref rek ren reo rer rfb rfc rfe rff rfk rfn rfo rfr rkb rkc rke rkf rkk rko rnb rnc rnn rno rnr rob roc roe rof rok ron roo ror rrb rrc rrf rrk rrn rrr