a-a a-b aaa aab aaf aag aao aay ab- aba abb abf abg abo aby af- afa afb aff afg afo afy ag- aga agb agf agg ago agy aoa aob aof aog aoo ay- aya ayf ayo baa bab baf bag bao bay bba bbb bbf bbg bbo bby bfa bfb bff bfg bfo bfy bga bgb bgf bgg bgo boa bob bof bog boo boy by- bya byf byg byo faa fab faf fag fao fay fba fbb fbf fbg fbo ffa fff ffg ffo ffy fga fgb fgf fgg foa fob fof fog foo foy fy- fya fyb fyo gaa gab gaf gag gao gay gba gbf gbg gbo gby gfa gfb gff gfo gfy gga ggb ggg ggo goa gob gof gog goo goy gy- gya gyb gyf gyo oaa oab oaf oag oao ob- oba obb obf obg obo oby of- ofa ofb off ofg ofo oga ogf ogg ogo ogy oo- ooa oob oof oog ooo oya oyo yaa yab yaf yag yao yay ybf ybg yby yfa yff yga ygo yob yof yog yoo yoy yyb yyf yyg yyy