c-- ccc ccd ccf cco ccr ccs cdc cdd cdf cdo cdr cds cfc cfd cff cfo cfr cfs co- coc cod cof coo cor cos crc crd crf cro crr crs csc csd csf cso csr css dcc dcd dcf dco dcr dcs ddc ddd ddf ddo ddr dds dfc dfd dff dfo dfr dfs doc dod dof doo dor dos drc drd dro drr drs dsc dsd dsf dso dsr dss fcc fcd fcf fco fcr fcs fdc fdd fdf fdo fdr fds ffc ffd fff ffo ffr ffs foc fof foo for fos frc frd frf fro frr frs fsc fsd fsf fso fsr fss oc- occ ocd ocf oco ocr ocs odc odd odf odo odr ods of- ofc ofd off ofo ofr ofs oo- ooc ood oof ooo oor oos or- orc ord orf oro orr ors os- osc osd osf oso osr oss rcc rcd rcf rco rcr rcs rdc rdd rdf rdo rdr rds rfc rfd rff rfo rfr rfs roc rod rof roo ror ros rrc rrd rrf rrr rrs rsc rsd rsf rso rsr rss scc scd scf sco scr scs sdc sdd sdf sdo sdr sds sfc sfd sff sfo sfr sfs soc sod sof soo sor sos sr- src srd srf sro srr srs ss- ssc ssd ssf sso ssr sss