c-- ccc ccd cck cco ccr ccs cdc cdd cdk cdo cdr cds ckc ckd cko cks co- coc cod cok coo cor cos crc crd crk cro crr crs csc csd csk cso csr css dcc dcd dck dco dcr dcs ddc ddd ddk ddo ddr dds dkc dkk dko dkr dks doc dod dok doo dor dos drc drd drk dro drr drs dsc dsd dsk dso dsr dss kcc kcd kck kcr kcs kdc kdk kdo kdr kds kkc kkk kkr kks koc kod kok koo kor kos krc krd krk kro krr krs ksc ksd ksk kso ksr kss oc- occ ocd ock oco ocr ocs odc odd odo odr ods okc okd okk oko okr oks oo- ooc ood ook ooo oor oos or- orc ord ork oro orr ors os- osc osd osk oso osr oss rcc rcd rco rcr rcs rdc rdd rdo rdr rds rkc rkk rko rks roc rod rok roo ror ros rrc rrd rrk rrr rrs rsc rsd rsk rso rsr rss scc scd sck sco scr scs sdc sdd sdk sdo sdr sds sk- skc skd skk sko skr sks soc sod sok soo sor sos sr- src srd srk sro srr srs ss- ssc ssd ssk sso ssr sss