c-- ccc ccd cck cco ccs cdc cdd cdk cdo cds ckc ckd cko cks co- coc cod cok coo cos csc csd csk cso css dcc dcd dck dco dcs ddc ddd ddk ddo dds dkc dkk dko dks doc dod dok doo dos dsc dsd dsk dso dss kcc kcd kck kcs kdc kdk kdo kds kkc kkk kks koc kod kok koo kos ksc ksd ksk kso kss oc- occ ocd ock oco ocs odc odd odo ods okc okd okk oko oks oo- ooc ood ook ooo oos os- osc osd osk oso oss scc scd sck sco scs sdc sdd sdk sdo sds sk- skc skd skk sko sks soc sod sok soo sos ss- ssc ssd ssk sso sss