c-- ccc cck cco ccr ccv ckc cko co- coc cok coo cor cov crc crk cro crr crv cvc cvk cvo cvr cvv kcc kck kcr kkc kkk kkr kkv koc kok koo kor krc krk kro krr krv kvk kvo kvr kvv oc- occ ock oco ocr ocv okc okk oko okr oo- ooc ook ooo oor oov or- orc ork oro orr orv ov- ovc ovo ovv rcc rco rcr rcv rkc rkk rko rkv roc rok roo ror rov rrc rrk rrr rvc rvo rvr rvv vcc vco vcr voc vok voo vor vov vrc vrk vrr vvc vvo vvr vvv