c-- ccc ccd cco ccs ccx cdc cdd cdo cds cdx co- coc cod coo cos cox csc csd cso css csx cxc cxo cxs cxx dcc dcd dco dcs dcx ddc ddd ddo dds ddx doc dod doo dos dox dsc dsd dso dss dsx dxc dxd dxo dxs dxx oc- occ ocd oco ocs ocx odc odd odo ods oo- ooc ood ooo oos oox os- osc osd oso oss osx ox- oxc oxo oxx scc scd sco scs scx sdc sdd sdo sds soc sod soo sos sox ss- ssc ssd sso sss ssx sxc sxs xcd xcx xdc xds xoc xod xoo xos xox xsc xss xxo xxx