-er c-- ccc ccd cce ccf cco ccr cdc cdd cde cdf cdo cdr ce- cec ced cee cef ceo cer cfc cfd cfe cff cfo cfr co- coc cod coe cof coo cor crc crd cre crf cro crr dcc dcd dce dcf dco dcr ddc ddd dde ddf ddo ddr de- dec ded dee def deo der dfc dfd dfe dff dfo dfr doc dod doe dof doo dor drc drd dre dro drr ec- ecc ecd ece ecf eco ecr ed- edc edd ede edf edo edr eec eed eee eef eeo eer ef- efc efd efe eff efo efr eo- eoc eod eoe eof eoo eor erc erd ere erf ero err fcc fcd fce fcf fco fcr fdc fdd fde fdf fdo fdr fec fed fee fef feo fer ffc ffd ffe fff ffo ffr foc foe fof foo for frc frd fre frf fro frr oc- occ ocd ocf oco ocr odc odd ode odf odo odr oec oed oee oef oeo oer of- ofc ofd ofe off ofo ofr oo- ooc ood oof ooo oor or- orc ord ore orf oro orr rcc rcd rce rcf rco rcr rdc rdd rde rdf rdo rdr re- rec red ree ref reo rer rfc rfd rfe rff rfo rfr roc rod roe rof roo ror rrc rrd rrf rrr