">      </span><span class="k">return</span>
<span class="k">   endif</span>
<span class="k">   do </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="nb">len</span>
<span class="nb">      </span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span>
<span class="w">      </span><span class="n">d</span><span