a-a a-b a-t aaa aab aad aaf aat aay ab- aba abb abd abf abt aby ad- ada adb add adf adt ady af- afa afb afd aff aft afy at- ata atb atd atf att ay- aya ayd ayf ayt baa bab bad baf bat bay bba bbb bbd bbf bbt bby bda bdb bdd bdf bdt bdy bfa bfb bfd bff bft bfy bta btb btd btf btt bty by- bya byd byf byt daa dab dad daf dat day dba dbb dbd dbf dbt dby dda ddb ddd ddf ddt ddy dfa dfb dfd dff dft dta dtb dtd dtf dtt dty dy- dya dyb dyd dyy faa fab fad faf fat fay fba fbb fbd fbf fbt fda fdb fdd fdf fdt ffa ffd fff fft ffy fta ftb ftd ftf ftt fty fy- fya fyb taa tab tad taf tat tay tba tbb tbd tbf tbt tda tdb tdd tdf tdt tdy tfa tfb tfd tff tft tta ttb ttd ttf ttt tty tya tyd tyf tyt yaa yab yad yaf yat yay ybf yby yda ydt ydy yfa yfd yff yft yta ytd ytf ytt yyb yyf yyt yyy