title: If ID has both values A and B it should return AB
body: <p>INPUT:</p>
  <pre><code>ID  VALUES
  1    A
  1    B
  2    A
  3    B
  </code></pre>
  <p>OUTPUT:</p>
  <pre><code>ID   VALUES
  1    AB
  1    AB
  2    A
  3    B
  </code></pre>
  <p>If ID has both values A and B it should return AB.</p>