c-- ccc ccf cco ccp ccx cfc cff cfo cfp cfx co- coc cof coo cop cox cpc cpf cpo cpp cpx cxc cxf cxo cxp cxx fcc fcf fco fcp fcx ffc fff ffo ffp ffx foc fof foo fop fox fpc fpo fpp fpx fxp fxx oc- occ ocf oco ocp ocx of- ofc off ofo ofp ofx oo- ooc oof ooo oop oox op- opc opf opo opp opx ox- oxc oxf oxo oxx p-p pcc pcf pco pcp pcx pfc pff pfo pfp pfx poc pof poo pop pox ppc ppf ppo ppp ppx pxc xcf xcp xcx xfx xoc xof xoo xop xox xpc xpf xpo xpp xxo xxp xxx