a-a a-b a-i aaa aab aaf aai aay ab- aba abb abf abi aby af- afa afb aff afi afy ai- aia aib aif aii aiy ay- aya ayf ayi baa bab baf bai bay bba bbb bbf bbi bby bfa bfb bff bfi bfy bi- bia bib bif bii biy by- bya byf byi faa fab faf fai fay fba fbb fbf fbi ffa fff ffi ffy fia fib fif fii fy- fya fyb fyi i-f ia- iaa iab iaf iai iba ibb ibf ibi iby ifa ifb iff ifi ify iia iib iif iii iya iyy yaa yab yaf yai yay ybf ybi yby yfa yff yif yii yyb yyf yyy