c-- ccc cck ccn cco ccs ckc cko cks cn- cnc cnn cno cns co- coc cok con coo cos csc csk csn cso css kcc kck kcn kcs kkc kkk kkn kks kn- knc knk knn kno koc kok kon koo kos ksc ksk ksn kso kss ncc nck ncn nco ncs nkc nkk nkn nko nks nnc nnk nnn nno nns no- noc nok non noo nos nsc nsk nsn nso nss oc- occ ock ocn oco ocs okc okk oko oks on- onc onk onn ono ons oo- ooc ook oon ooo oos os- osc osk osn oso oss scc sck scn sco scs sk- skc skk sko sks snc snk snn sno sns soc sok son soo sos ss- ssc ssk ssn sso sss