a-a a-b a-t aaa aab aao aas aat aay ab- aba abb abo abs abt aby aoa aob aoo aos aot as- asa asb aso ass ast asy at- ata atb ato ats att ay- aya ayo ays ayt baa bab bao bas bat bay bba bbb bbo bbs bbt bby boa bob boo bos bot boy bsa bsb bso bss bst bsy bta btb bto bts btt bty by- bya byo bys byt oaa oab oao oas oat ob- oba obb obo obs obt oby oo- ooa oob ooo oos oot os- osa osb oso oss ost ot- ota otb oto ots ott oya oyo oys saa sab sao sas sat say sba sbb sbo sbs sbt sby soa sob soo sos sot soy ss- ssa ssb sso sss sst sta stb sto sts stt sty sy- sya syb sys syt taa tab tao tas tat tay tba tbb tbo tbs tbt to- toa tob too tos tot toy tsa tsb tso tss tst tsy tta ttb tto tts ttt tty tya tyo tys tyt yaa yab yao yas yat yay ybs yby yob yoo yos yot yoy ysa ysb yso yss yst ysy yta yto yts ytt yyb yys yyt yyy