a-a a-b a-i aaa aab aad aaf aai ab- aba abb abd abf abi ad- ada adb add adf adi af- afa afb afd aff afi ai- aia aib aid aif aii baa bab bad baf bai bba bbb bbd bbf bbi bda bdb bdd bdf bdi bfa bfb bfd bff bfi bi- bia bib bid bif bii daa dab dad daf dai dba dbb dbd dbf dbi dda ddb ddd ddf ddi dfa dfb dfd dff dfi di- dia dib did dif dii faa fab fad faf fai fba fbb fbd fbf fbi fda fdb fdd fdf fdi ffa ffd fff ffi fia fib fid fif fii i-d i-f ia- iaa iab iad iaf iai iba ibb ibd ibf ibi ida idb idd idf idi ifa ifb ifd iff ifi iia iib iid iif iii