a-a a-b a-z aaa aab aad aaf aay aaz ab- aba abb abd abf aby abz ad- ada adb add adf ady adz af- afa afb afd aff afy afz ay- aya ayd ayf ayz az- aza azb azd azf azy azz baa bab bad baf bay baz bba bbb bbd bbf bby bda bdb bdd bdf bdy bdz bfa bfb bfd bff bfy bfz by- bya byd byf byz bza bzd bzf bzz daa dab dad daf day daz dba dbb dbd dbf dby dbz dda ddb ddd ddf ddy ddz dfa dfb dfd dff dfz dy- dya dyb dyd dyy dza dzb dzd faa fab fad faf fay faz fba fbb fbd fbf fda fdb fdd fdf ffa ffd fff ffy ffz fy- fya fyb fyz fzd yaa yab yad yaf yay yaz ybf yby ybz yda ydy yfa yfd yff yyb yyf yyy yyz yzb yzf yzy zaa zab zad zaf zay zaz zbb zby zdf zfa zfd zfy zzy zzz