a-a a-b a-c aaa aab aac aad aao aay ab- aba abb abc abd abo aby ac- aca acb acc acd aco acy ad- ada adb adc add ado ady aoa aob aoc aod aoo ay- aya ayc ayd ayo baa bab bac bad bao bay bba bbb bbc bbd bbo bby bca bcb bcc bcd bco bcy bda bdb bdc bdd bdo bdy boa bob boc bod boo boy by- bya byc byd byo c-- caa cab cac cad cao cay cba cbb cbc cbd cbo cby cca ccb ccc ccd cco cda cdb cdc cdd cdo cdy co- coa cob coc cod coo coy cya cyb cyc cyd cyo daa dab dac dad dao day dba dbb dbc dbd dbo dby dca dcb dcc dcd dco dda ddb ddc ddd ddo ddy doa dob doc dod doo doy dy- dya dyb dyc dyd dyo dyy oaa oab oac oad oao ob- oba obb obc obd obo oby oc- oca ocb occ ocd oco oda odb odc odd odo oo- ooa oob ooc ood ooo oya oyd oyo yaa yab yac yad yao yay ybc yby yca ycc ycd yco ycy yda ydo ydy yob yoc yod yoo yoy yyb yyc yyy