an>
                            <span class="p">)</span>
                        <span class="p">)</span>
                    <span class="p">)</span>
                    <span class="c1"># (2.3)</span>
                    <span class="n">solver</span><span class="o">.</span><span class="n">Add</span><span class="p">(</span>
                        <span class="p">((</span><span class="nb">sum</span><span class="p">([</span><span class="n">X</span><span class="p">[</span><span class="n">k</span> <span class