title: Regular Expression for Bit Strings Divisible by 4
body: <p>I am newbie to Regular Expression.</p>
  
  <p>In one of my homework problem, I have been ask to write the regular expression of  following.</p>
  
  <pre><code>The set of all bit strings (i.e. strings over alphabet {0,1}) that are divisible by 4.
  </code></pre>
  
  <p>Now, I am not getting how should I start to achieve solution. How to find bits divisible by 4?</p>