-er bbb bbd bbe bbr bbt bdb bdd bde bdr bdt be- beb bed bee ber bet brb brd bre brr brt btb btd bte btr btt dbb dbd dbe dbr dbt ddb ddd dde ddr ddt de- deb ded dee der det drb drd dre drr drt dtb dtd dte dtr dtt ebb ebd ebe ebr ebt ed- edb edd ede edr edt eeb eed eee eer eet erb erd ere err ert etb etd ete etr ett rbb rbd rbe rbr rbt rdb rdd rde rdr rdt re- reb red ree rer ret rrb rrd rrr rrt rtb rtd rte rtr rtt tbb tbd tbe tbr tbt tdb tdd tde tdr tdt te- teb ted tee ter tet trb trd tre trr trt ttb ttd tte ttr ttt