c-- ccc ccd cco ccs cct cdc cdd cdo cds cdt co- coc cod coo cos cot csc csd cso css cst ctc ctd cto cts ctt dcc dcd dco dcs dct ddc ddd ddo dds ddt doc dod doo dos dot dsc dsd dso dss dst dtc dtd dto dts dtt oc- occ ocd oco ocs oct odc odd odo ods odt oo- ooc ood ooo oos oot os- osc osd oso oss ost ot- otc otd oto ots ott scc scd sco scs sct sdc sdd sdo sds sdt soc sod soo sos sot ss- ssc ssd sso sss sst stc std sto sts stt tcc tcd tco tcs tct tdc tdd tdo tds tdt to- toc tod too tos tot tsc tsd tso tss tst ttc ttd tto tts ttt