title: OCaml - how to sort pairs?
body: <p>We have pairs:</p>
  
  <pre><code> (3,10000) (1,2),(2,11) (2,0) (2, 10) (1,1000000)
  </code></pre>
  
  <p>And we would like to order:</p>
  
  <pre><code> (1,2) (1,1000000), (2,0) (2, 10) (2,11) (3,10000)
  </code></pre>
  
  <p>How to do it in OCaml ?</p>