><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="n">l</span><span class="p">)</span>
<span class="w">         </span><span class="n">ti</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">ai</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="n">l</span><span class="p">)</span>
<span class="w">         </span><span class="k">if</span><span class="w"> </span><span clas