a-a a-b a-c aaa aab aac aan aao aay ab- aba abb abc abn abo aby ac- aca acb acc acn aco acy an- ana anb anc ann ano any aoa aob aoc aon aoo ay- aya ayc ayn ayo baa bab bac ban bao bay bba bbb bbc bbn bbo bby bca bcb bcc bcn bco bcy bna bnb bnc bnn bno boa bob boc bon boo boy by- bya byc byn byo c-- caa cab cac can cao cay cba cbb cbc cbn cbo cby cca ccb ccc ccn cco cn- cna cnb cnc cnn cno cny co- coa cob coc con coo coy cya cyb cyc cyn cyo naa nab nac nan nao nay nba nbb nbc nbn nbo nca ncb ncc ncn nco nna nnb nnc nnn nno no- noa nob noc non noo noy nya nyc nyn nyo nyy oaa oab oac oan oao ob- oba obb obc obn obo oby oc- oca ocb occ ocn oco on- ona onb onc onn ono ony oo- ooa oob ooc oon ooo oya oyo yaa yab yac yan yao yay ybc yby yca ycc yco ycy yna ynn yny yob yoc yon yoo yoy yyb yyc yyy