-er c-- ccc ccd cce cck cco ccr cdc cdd cde cdk cdo cdr ce- cec ced cee cek ceo cer ckc ckd cko co- coc cod coe cok coo cor crc crd cre crk cro crr dcc dcd dce dck dco dcr ddc ddd dde ddk ddo ddr de- dec ded dee dek deo der dkc dke dkk dko dkr doc dod doe dok doo dor drc drd dre drk dro drr ec- ecc ecd ece eck eco ecr ed- edc edd ede edk edo edr eec eed eee eek eeo eer ekc ekd eke eko ekr eo- eoc eod eoe eok eoo eor erc erd ere erk ero err kcc kcd kce kck kcr kdc kde kdk kdo kdr ke- kec ked kee kek keo ker kkc kke kkk kkr koc kod koe kok koo kor krc krd krk kro krr oc- occ ocd ock oco ocr odc odd ode odo odr oec oed oee oeo oer okc okd oke okk oko okr oo- ooc ood ook ooo oor or- orc ord ore ork oro orr rcc rcd rce rco rcr rdc rdd rde rdo rdr re- rec red ree rek reo rer rkc rke rkk rko roc rod roe rok roo ror rrc rrd rrk rrr