a-a a-b a-i aaa aab aaf aai aan ab- aba abb abf abi abn af- afa afb aff afi afn ai- aia aib aif aii ain an- ana anb anf ani ann baa bab baf bai ban bba bbb bbf bbi bbn bfa bfb bff bfi bfn bi- bia bib bif bii bin bna bnb bnf bni bnn faa fab faf fai fan fba fbb fbf fbi fbn ffa fff ffi ffn fia fib fif fii fin fna fnb fnf fni fnn i-f ia- iaa iab iaf iai ian iba ibb ibf ibi ibn ifa ifb iff ifi ifn iia iib iif iii iin in- ina inb inf ini inn n-i naa nab naf nai nan nba nbb nbf nbi nbn nfa nfb nff nfi nfn nia nib nif nii nin nna nnb nnf nni nnn