-er bbb bbd bbe bbr bbs bdb bdd bde bdr bds be- beb bed bee ber bes brb brd bre brr brs bsb bsd bse bsr bss dbb dbd dbe dbr dbs ddb ddd dde ddr dds de- deb ded dee der des drb drd dre drr drs dsb dsd dse dsr dss ebb ebd ebe ebr ebs ed- edb edd ede edr eds eeb eed eee eer ees erb erd ere err ers es- esb esd ese esr ess rbb rbd rbe rbr rbs rdb rdd rde rdr rds re- reb red ree rer res rrb rrd rrr rrs rsb rsd rse rsr rss sbb sbd sbe sbr sbs sdb sdd sde sdr sds se- seb sed see ser ses sr- srb srd sre srr srs ss- ssb ssd sse ssr sss