-er c-- ccc cce ccf cck cco ccr ce- cec cee cef cek ceo cer cfc cfe cff cfk cfo cfr ckc cko co- coc coe cof cok coo cor crc cre crf crk cro crr ec- ecc ece ecf eck eco ecr eec eee eef eek eeo eer ef- efc efe eff efo efr ekc eke ekf eko ekr eo- eoc eoe eof eok eoo eor erc ere erf erk ero err fcc fce fcf fck fco fcr fec fee fef fek feo fer ffc ffe fff ffk ffo ffr fkc fkf fkk foc foe fof fok foo for frc fre frf frk fro frr kcc kce kck kcr ke- kec kee kef kek keo ker kfc kff kfo kkc kke kkk kkr koc koe kof kok koo kor krc krf krk kro krr oc- occ ocf ock oco ocr oec oee oef oeo oer of- ofc ofe off ofo ofr okc oke okk oko okr oo- ooc oof ook ooo oor or- orc ore orf ork oro orr rcc rce rcf rco rcr re- rec ree ref rek reo rer rfc rfe rff rfk rfo rfr rkc rke rkf rkk rko roc roe rof rok roo ror rrc rrf rrk rrr