title: How to find most common element in list, and if there's a tie, the one who's last occurance is first?
body: <p>Basically if given a list </p>
  
  <pre><code>events = [123,123,456,456,456,123]
  </code></pre>
  
  <p>I expect it <em>returns</em> <strong>456</strong> because 456 was last seen earlier than 123 was last seen.</p>
  
  <p>I made lists comprised of the counts and indices of the initial list of numbers.
  I also made a dictionary in which the key is the element from events (original part) and hte value is the <code>.count()</code> of the key.  </p>
  
  <p>I don't really know where to go from here and could use some help.</p>