b-u bbb bbr bbs bbu bby brb brr brs bru bry bsb bsr bss bsu bsy bub bur bus buu buy by- byr bys byu rbb rbr rbs rbu rrb rrr rrs rru rsb rsr rss rsu rub rur rus ruu ruy ry- ryr rys ryu ryy sbb sbr sbs sbu sby sr- srb srr srs sry ss- ssb ssr sss ssu sub sur sus suu suy sy- syb syr sys syu ubb ubr ubs ubu uby ur- urb urr urs uru ury usb usr uss usu uur uus uuu uys uyu ybr ybs yby yrs yru ysb ysr yss ysu ysy yur yus yuu yuy yyb yys yyu yyy