title: auto space between divs
body: <p>I have to create a web page with a big div (grey colored) and many divs (black colored) near it (float left).</p>
  
  <p><img src="https://i.imgur.com/sCbWf.png" alt=""></p>
  
  <p>At the moment I'm using a margin (<code>margin-right</code>) which divides the black divs.
  (I don't mind about the grey div because it's done.)
  My problem is that the most right div for each row must not have the <code>margin-right</code> because i haven't got any more space to give it.
  I can't create a specific class (<code>margin-right: 0</code>) for them because all the black divs will be added dynamically.
  Is there any solution to my problem?</p>