a-a a-b aaa aab aao aar aav aay ab- aba abb abo abr abv aby aoa aob aoo aor aov ar- ara arb aro arr arv ary av- ava avb avo avr avy ay- aya ayo ayr baa bab bao bar bav bay bba bbb bbo bbr bby boa bob boo bor bov boy bra brb bro brr brv bry bva bvb bvo bvr bvv by- bya byo byr oaa oab oao oar oav ob- oba obb obo obr obv oby oo- ooa oob ooo oor oov or- ora orb oro orr orv ory ov- ova ovb ovo ovv oya oyo ra- raa rab rao rar rav ray rba rbb rbo rbr roa rob roo ror rov roy rra rrb rrr rva rvb rvo rvr rvv rvy ry- rya ryo ryr ryy v-a vaa vab vao var vav vay vba vbo vbr vbv voa vob voo vor vov voy vra vrb vrr vry vva vvb vvo vvr vvv yaa yab yao yar yav yay ybr yby yob yoo yor yoy yra yro yva yvo yvr yvy yyb yyy