title: Ruby - Parsing '(3)' to integer returns 0
body: <p>I'm trying to get integer from string <code>'(3)'</code>. However method <code>to_i</code> returns <code>0</code>. 
  It seems that brackets with quotes cause the problem, but I don't understand the reason. </p>
  
  <pre><code>'3'.to_i =&gt; 3
  (3).to_i =&gt; 3
  '(3)'.to_i =&gt; 0
  </code></pre>
  
  <p>Why does it happen and how to solve it? Thank you!</p>