a-a a-c aaa aac aaf aao aar ac- aca acc acf aco acr af- afa afc aff afo afr aoa aoc aof aoo aor ar- ara arc arf aro arr c-- caa cac caf cao car cca ccc ccf cco ccr cfa cfc cff cfo cfr co- coa coc cof coo cor cra crc crf cro crr faa fac faf fao far fca fcc fcf fco fcr ffa ffc fff ffo ffr foa foc fof foo for fra frc frf fro frr oaa oac oaf oao oar oc- oca occ ocf oco ocr of- ofa ofc off ofo ofr oo- ooa ooc oof ooo oor or- ora orc orf oro orr ra- raa rac raf rao rar rca rcc rcf rco rcr rfa rfc rff rfo rfr roa roc rof roo ror rra rrc rrf rrr