a-a a-b a-c aaa aab aac aag aao aay ab- aba abb abc abg abo aby ac- aca acb acc acg aco acy ag- aga agb agc agg ago agy aoa aob aoc aog aoo ay- aya ayc ayo baa bab bac bag bao bay bba bbb bbc bbg bbo bby bca bcb bcc bcg bco bcy bga bgb bgc bgg bgo boa bob boc bog boo boy by- bya byc byg byo c-- caa cab cac cag cao cay cba cbb cbc cbg cbo cby cca ccb ccc ccg cco cga cgb cgc cgg cgo cgy co- coa cob coc cog coo coy cya cyb cyc cyg cyo gaa gab gac gag gao gay gba gbc gbg gbo gby gca gcb gcc gcg gco gga ggb ggc ggg ggo goa gob goc gog goo goy gy- gya gyb gyo oaa oab oac oag oao ob- oba obb obc obg obo oby oc- oca ocb occ ocg oco oga ogc ogg ogo ogy oo- ooa oob ooc oog ooo oya oyo yaa yab yac yag yao yay ybc ybg yby yca ycc yco ycy yga ygc ygo yob yoc yog yoo yoy yyb yyc yyg yyy