c-- ccc ccd ccf cco ccr cdc cdd cdf cdo cdr cfc cfd cff cfo cfr co- coc cod cof coo cor crc crd crf cro crr dcc dcd dcf dco dcr ddc ddd ddf ddo ddr dfc dfd dff dfo dfr doc dod dof doo dor drc drd dro drr fcc fcd fcf fco fcr fdc fdd fdf fdo fdr ffc ffd fff ffo ffr foc fof foo for frc frd frf fro frr oc- occ ocd ocf oco ocr odc odd odf odo odr of- ofc ofd off ofo ofr oo- ooc ood oof ooo oor or- orc ord orf oro orr rcc rcd rcf rco rcr rdc rdd rdf rdo rdr rfc rfd rff rfo rfr roc rod rof roo ror rrc rrd rrf rrr