a-a a-b a-i aaa aab aaf aai aak aan ab- aba abb abf abi abk abn af- afa afb aff afi afk afn ai- aia aib aif aii aik ain aka akb aki akk akn an- ana anb anf ani ank ann baa bab baf bai bak ban bba bbb bbf bbi bbk bbn bfa bfb bff bfi bfn bi- bia bib bif bii bik bin bka bkb bkf bkk bkn bna bnb bnf bni bnk bnn faa fab faf fai fak fan fba fbb fbf fbi fbk fbn ffa fff ffi ffk ffn fia fib fif fii fik fin fka fkb fkf fki fkk fna fnb fnf fni fnk fnn i-f ia- iaa iab iaf iai ian iba ibb ibf ibi ibk ibn ifa ifb iff ifi ifn iia iib iif iii iin ika ikb ikf iki ikk in- ina inb inf ini ink inn ka- kaa kab kaf kai kak kan kba kbb kbf kbi kbk kbn kfa kff kfi kia kib kif kii kik kin kkb kki kkk kkn kn- kna knf kni knk knn n-i naa nab naf nai nak nan nba nbb nbf nbi nbk nbn nfa nfb nff nfi nfk nfn nia nib nif nii nik nin nka nkf nki nkk nkn nna nnb nnf nni nnk nnn