c-- ccc ccf cco ccs cct cfc cff cfo cfs cft co- coc cof coo cos cot csc csf cso css cst ctc ctf cto cts ctt fcc fcf fco fcs fct ffc fff ffo ffs fft foc fof foo fos fot fsc fsf fso fss fst ftc ftf fto fts ftt oc- occ ocf oco ocs oct of- ofc off ofo ofs oft oo- ooc oof ooo oos oot os- osc osf oso oss ost ot- otc otf oto ots ott scc scf sco scs sct sfc sff sfo sfs sft soc sof soo sos sot ss- ssc ssf sso sss sst stc stf sto sts stt tcc tcf tco tcs tct tfc tff tfo tfs tft to- toc tof too tos tot tsc tsf tso tss tst ttc ttf tto tts ttt