a-a a-b aaa aab aad aaf aao aay ab- aba abb abd abf abo aby ad- ada adb add adf ado ady af- afa afb afd aff afo afy aoa aob aod aof aoo ay- aya ayd ayf ayo baa bab bad baf bao bay bba bbb bbd bbf bbo bby bda bdb bdd bdf bdo bdy bfa bfb bfd bff bfo bfy boa bob bod bof boo boy by- bya byd byf byo daa dab dad daf dao day dba dbb dbd dbf dbo dby dda ddb ddd ddf ddo ddy dfa dfb dfd dff dfo doa dob dod dof doo doy dy- dya dyb dyd dyo dyy faa fab fad faf fao fay fba fbb fbd fbf fbo fda fdb fdd fdf fdo ffa ffd fff ffo ffy foa fob fof foo foy fy- fya fyb fyo oaa oab oad oaf oao ob- oba obb obd obf obo oby oda odb odd odf odo of- ofa ofb ofd off ofo oo- ooa oob ood oof ooo oya oyd oyo yaa yab yad yaf yao yay ybf yby yda ydo ydy yfa yfd yff yob yod yof yoo yoy yyb yyf yyy