a-a a-b a-t aaa aab aaf aao aat aay ab- aba abb abf abo abt aby af- afa afb aff afo aft afy aoa aob aof aoo aot at- ata atb atf ato att ay- aya ayf ayo ayt baa bab baf bao bat bay bba bbb bbf bbo bbt bby bfa bfb bff bfo bft bfy boa bob bof boo bot boy bta btb btf bto btt bty by- bya byf byo byt faa fab faf fao fat fay fba fbb fbf fbo fbt ffa fff ffo fft ffy foa fob fof foo fot foy fta ftb ftf fto ftt fty fy- fya fyb fyo oaa oab oaf oao oat ob- oba obb obf obo obt oby of- ofa ofb off ofo oft oo- ooa oob oof ooo oot ot- ota otb otf oto ott oya oyo taa tab taf tao tat tay tba tbb tbf tbo tbt tfa tfb tff tfo tft to- toa tob tof too tot toy tta ttb ttf tto ttt tty tya tyf tyo tyt yaa yab yaf yao yat yay ybf yby yfa yff yft yob yof yoo yot yoy yta ytf yto ytt yyb yyf yyt yyy