c-- ccc ccf cck cco ccr cct cfc cff cfk cfo cfr cft ckc cko ckt co- coc cof cok coo cor cot crc crf crk cro crr crt ctc ctf ctk cto ctr ctt fcc fcf fck fco fcr fct ffc fff ffk ffo ffr fft fkc fkf fkk fkt foc fof fok foo for fot frc frf frk fro frr frt ftc ftf ftk fto ftr ftt k-t kcc kck kcr kct kfc kff kfo kkc kkk kkr kkt koc kof kok koo kor kot krc krf krk kro krr krt ktc ktf ktk kto ktr ktt oc- occ ocf ock oco ocr oct of- ofc off ofo ofr oft okc okk oko okr oo- ooc oof ook ooo oor oot or- orc orf ork oro orr ort ot- otc otf otk oto otr ott rcc rcf rco rcr rct rfc rff rfk rfo rfr rft rkc rkf rkk rko rkt roc rof rok roo ror rot rrc rrf rrk rrr rrt rtc rtf rtk rto rtr rtt tcc tcf tck tco tcr tct tfc tff tfk tfo tfr tft tkc tkk tko tkr tkt to- toc tof tok too tor tot trc trf trk tro trr trt ttc ttf ttk tto ttr ttt