title: find the only unpaired element in the array
body: <p>Accenture interview question:</p>
  
  <p>You have been given an array of size <code>2n+1</code> that have <code>n</code> pair of integers (can be <code>+ve</code>, <code>-ve</code> or <code>0</code>) and one unpaired element.</p>
  
  <p>How would you find the unpaired element?</p>
  
  <p>Pair means <strong>duplicate</strong>. So <code>(3,3)</code> is a pair and <code>(3,-3)</code> is <strong>not</strong> a pair.</p>