c-- ccc ccf cco ccr cct cfc cff cfo cfr cft co- coc cof coo cor cot crc crf cro crr crt ctc ctf cto ctr ctt fcc fcf fco fcr fct ffc fff ffo ffr fft foc fof foo for fot frc frf fro frr frt ftc ftf fto ftr ftt oc- occ ocf oco ocr oct of- ofc off ofo ofr oft oo- ooc oof ooo oor oot or- orc orf oro orr ort ot- otc otf oto otr ott rcc rcf rco rcr rct rfc rff rfo rfr rft roc rof roo ror rot rrc rrf rrr rrt rtc rtf rto rtr rtt tcc tcf tco tcr tct tfc tff tfo tfr tft to- toc tof too tor tot trc trf tro trr trt ttc ttf tto ttr ttt