-er ddd dde ddr ddt ddx de- ded dee der det dex drd dre drr drt drx dtd dte dtr dtt dtx dxd dxr dxt dxx ed- edd ede edr edt edx eed eee eer eet eex erd ere err ert etd ete etr ett etx ex- exd exe exr ext exx rdd rde rdr rdt rdx re- red ree rer ret rex rrd rrr rrt rtd rte rtr rtt rtx rxr t-x tdd tde tdr tdt tdx te- ted tee ter tet tex trd tre trr trt trx ttd tte ttr ttt ttx txe txt xde xdr xdt xed xee xer xet xex xrd xrt xrx xtr xtx xxx