c-- ccc cck cco ccs cct ckc cko cks ckt co- coc cok coo cos cot csc csk cso css cst ctc ctk cto cts ctt k-t kcc kck kcs kct kkc kkk kks kkt koc kok koo kos kot ksc ksk kso kss kst ktc ktk kto kts ktt oc- occ ock oco ocs oct okc okk oko oks oo- ooc ook ooo oos oot os- osc osk oso oss ost ot- otc otk oto ots ott scc sck sco scs sct sk- skc skk sko sks skt soc sok soo sos sot ss- ssc ssk sso sss sst stc stk sto sts stt tcc tck tco tcs tct tkc tkk tko tks tkt to- toc tok too tos tot tsc tsk tso tss tst ttc ttk tto tts ttt