bbb bbd bbo bbr bbs bdb bdd bdo bdr bds bob bod boo bor bos brb brd bro brr brs bsb bsd bso bsr bss dbb dbd dbo dbr dbs ddb ddd ddo ddr dds dob dod doo dor dos drb drd dro drr drs dsb dsd dso dsr dss ob- obb obd obo obr obs odb odd odo odr ods oo- oob ood ooo oor oos or- orb ord oro orr ors os- osb osd oso osr oss rbb rbd rbo rbr rbs rdb rdd rdo rdr rds rob rod roo ror ros rrb rrd rrr rrs rsb rsd rso rsr rss sbb sbd sbo sbr sbs sdb sdd sdo sdr sds sob sod soo sor sos sr- srb srd sro srr srs ss- ssb ssd sso ssr sss