title: Common elements between two lists not using sets in Python
body: <p>I want count the same elements of two lists. Lists can have duplicate elements, so I can't convert this to sets and use &amp; operator.</p>
  
  <pre><code>a=[2,2,1,1]
  b=[1,1,3,3]
  </code></pre>
  
  <p>set(a) &amp; set(b) work<br>
  a &amp; b don't work  </p>
  
  <p>It is possible to do it withoud set and dictonary?</p>