a-a a-b a-t aaa aab aao aar aat aay ab- aba abb abo abr abt aby aoa aob aoo aor aot ar- ara arb aro arr art ary at- ata atb ato atr att ay- aya ayo ayr ayt baa bab bao bar bat bay bba bbb bbo bbr bbt bby boa bob boo bor bot boy bra brb bro brr brt bry bta btb bto btr btt bty by- bya byo byr byt oaa oab oao oar oat ob- oba obb obo obr obt oby oo- ooa oob ooo oor oot or- ora orb oro orr ort ory ot- ota otb oto otr ott oya oyo ra- raa rab rao rar rat ray rba rbb rbo rbr rbt roa rob roo ror rot roy rra rrb rrr rrt rta rtb rto rtr rtt rty ry- rya ryo ryr ryy taa tab tao tar tat tay tba tbb tbo tbr tbt to- toa tob too tor tot toy tra trb tro trr trt try tta ttb tto ttr ttt tty tya tyo tyr tyt yaa yab yao yar yat yay ybr yby yob yoo yor yot yoy yra yro yrt yta yto ytr ytt yyb yyt yyy