b-u bbb bbd bbr bbs bbu bdb bdd bdr bds bdu brb brd brr brs bru bsb bsd bsr bss bsu bub bud bur bus buu dbb dbd dbr dbs dbu ddb ddd ddr dds ddu drb drd drr drs dru dsb dsd dsr dss dsu dub dud dur dus rbb rbd rbr rbs rbu rdb rdd rdr rds rdu rrb rrd rrr rrs rru rsb rsd rsr rss rsu rub rud rur rus ruu sbb sbd sbr sbs sbu sdb sdd sdr sds sdu sr- srb srd srr srs ss- ssb ssd ssr sss ssu sub sud sur sus suu ubb ubr ubs ubu udb udd udr uds udu ur- urb urd urr urs uru usb usd usr uss usu uur uus uuu