a-a a-c aaa aac aaf aan aao ac- aca acc acf acn aco af- afa afc aff afn afo an- ana anc anf ann ano aoa aoc aof aon aoo c-- caa cac caf can cao cca ccc ccf ccn cco cfa cfc cff cfn cfo cn- cna cnc cnf cnn cno co- coa coc cof con coo faa fac faf fan fao fca fcc fcf fcn fco ffa ffc fff ffn ffo fna fnc fnf fnn foa foc fof fon foo naa nac naf nan nao nca ncc ncf ncn nco nfa nfc nff nfn nfo nna nnc nnf nnn nno no- noa noc nof non noo oaa oac oaf oan oao oc- oca occ ocf ocn oco of- ofa ofc off ofn ofo on- ona onc onf onn ono oo- ooa ooc oof oon ooo