title: Remove the last element in a queue
body: <p>I need to remove the last element of a queue.
  The only operations I may use are</p>
  <ul>
  <li><code>Peek()</code> - get the first element without removing it</li>
  <li><code>Enqueue(element)</code> - Insert an element to the back of the queue</li>
  <li><code>Dequeue()</code> - Remove the first element</li>
  <li><code>IsEmpty()</code> - true or false whether the queue is empty.</li>
  </ul>
  <p>And I can't use arrays or queues, and the number of elements is not available.</p>
  <p>I thought of some solutions, but each time I get stuck, since I don't know how to tell if the current element is the last element.</p>