span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">n</span>
<span class="w">         </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">xr</span><span class="p">(</span><span class="n">ix</span><span class="p">)</span><span class="o">*</span><span class="n">yi</s