c-- ccc ccd ccf cck cco ccr cdc cdd cdf cdk cdo cdr cfc cfd cff cfk cfo cfr ckc ckd cko co- coc cod cof cok coo cor crc crd crf crk cro crr dcc dcd dcf dck dco dcr ddc ddd ddf ddk ddo ddr dfc dfd dff dfk dfo dfr dkc dkk dko dkr doc dod dof dok doo dor drc drd drk dro drr fcc fcd fcf fck fco fcr fdc fdd fdf fdk fdo fdr ffc ffd fff ffk ffo ffr fkc fkf fkk foc fof fok foo for frc frd frf frk fro frr kcc kcd kck kcr kdc kdf kdk kdo kdr kfc kfd kff kfo kkc kkk kkr koc kod kof kok koo kor krc krd krf krk kro krr oc- occ ocd ocf ock oco ocr odc odd odf odo odr of- ofc ofd off ofo ofr okc okd okk oko okr oo- ooc ood oof ook ooo oor or- orc ord orf ork oro orr rcc rcd rcf rco rcr rdc rdd rdf rdo rdr rfc rfd rff rfk rfo rfr rkc rkf rkk rko roc rod rof rok roo ror rrc rrd rrf rrk rrr