a-a aaa aaf aak aan aao af- afa aff afk afn afo aka akk akn ako an- ana anf ank ann ano aoa aof aok aon aoo faa faf fak fan fao ffa fff ffk ffn ffo fka fkf fkk fna fnf fnk fnn foa fof fok fon foo ka- kaa kaf kak kan kao kfa kff kfo kkk kkn kn- kna knf knk knn kno koa kof kok kon koo naa naf nak nan nao nfa nff nfk nfn nfo nka nkf nkk nkn nko nna nnf nnk nnn nno no- noa nof nok non noo oaa oaf oak oan oao of- ofa off ofn ofo oka okk oko on- ona onf onk onn ono oo- ooa oof ook oon ooo