a-a a-b a-i aaa aab aaf aai aak aay ab- aba abb abf abi abk aby af- afa afb aff afi afk afy ai- aia aib aif aii aik aiy aka akb aki akk ay- aya ayf ayi ayk baa bab baf bai bak bay bba bbb bbf bbi bbk bby bfa bfb bff bfi bfy bi- bia bib bif bii bik biy bka bkb bkf bkk by- bya byf byi byk faa fab faf fai fak fay fba fbb fbf fbi fbk ffa fff ffi ffk ffy fia fib fif fii fik fka fkb fkf fki fkk fy- fya fyb fyi fyk i-f ia- iaa iab iaf iai iba ibb ibf ibi ibk iby ifa ifb iff ifi ify iia iib iif iii ika ikb ikf iki ikk iya iyy ka- kaa kab kaf kai kak kay kba kbb kbf kbi kbk kfa kff kfi kia kib kif kii kik kkb kki kkk kky kya yaa yab yaf yai yak yay ybf ybi yby yfa yff yif yii yka yki ykk yyb yyf yyy