bbb bbd bbr bbs bbt bdb bdd bdr bds bdt brb brd brr brs brt bsb bsd bsr bss bst btb btd btr bts btt dbb dbd dbr dbs dbt ddb ddd ddr dds ddt drb drd drr drs drt dsb dsd dsr dss dst dtb dtd dtr dts dtt rbb rbd rbr rbs rbt rdb rdd rdr rds rdt rrb rrd rrr rrs rrt rsb rsd rsr rss rst rtb rtd rtr rts rtt sbb sbd sbr sbs sbt sdb sdd sdr sds sdt sr- srb srd srr srs srt ss- ssb ssd ssr sss sst stb std str sts stt tbb tbd tbr tbs tbt tdb tdd tdr tds tdt trb trd trr trs trt tsb tsd tsr tss tst ttb ttd ttr tts ttt