title: How to find all positions of the maximum value in a list?
body: <p>I have a list:</p>
  
  <pre><code>a = [32, 37, 28, 30, 37, 25, 27, 24, 35, 55, 23, 31, 55, 21, 40, 18, 50,
               35, 41, 49, 37, 19, 40, 41, 31]
  </code></pre>
  
  <p>max element is 55 (two elements on position 9 and 12)</p>
  
  <p>I need to find on which position(s) the maximum value is situated. Please, help.</p>