-er c-- ccc ccd cce ccf cck ccr cdc cdd cde cdf cdk cdr ce- cec ced cee cef cek cer cfc cfd cfe cff cfk cfr ckc ckd crc crd cre crf crk crr dcc dcd dce dcf dck dcr ddc ddd dde ddf ddk ddr de- dec ded dee def dek der dfc dfd dfe dff dfk dfr dkc dke dkk dkr drc drd dre drk drr ec- ecc ecd ece ecf eck ecr ed- edc edd ede edf edk edr eec eed eee eef eek eer ef- efc efd efe eff efr ekc ekd eke ekf ekr erc erd ere erf erk err fcc fcd fce fcf fck fcr fdc fdd fde fdf fdk fdr fec fed fee fef fek fer ffc ffd ffe fff ffk ffr fkc fkf fkk frc frd fre frf frk frr kcc kcd kce kck kcr kdc kde kdf kdk kdr ke- kec ked kee kef kek ker kfc kfd kff kkc kke kkk kkr krc krd krf krk krr rcc rcd rce rcf rcr rdc rdd rde rdf rdr re- rec red ree ref rek rer rfc rfd rfe rff rfk rfr rkc rke rkf rkk rrc rrd rrf rrk rrr