b-u bbb bbo bbr bbu bby bob boo bor bou boy brb bro brr bru bry bub buo bur buu buy by- byo byr byu ob- obb obo obr obu oby oo- oob ooo oor or- orb oro orr oru ory ou- ouo our oyo rbb rbo rbr rbu rob roo ror rou roy rrb rrr rru rub ruo rur ruu ruy ry- ryo ryr ryu ryy ubb ubo ubr ubu uby uob uoo uor ur- urb uro urr uru ury uur uuu uyo uyu ybr yby yob yoo yor you yoy yro yru yuo yur yuu yuy yyb yyu yyy