title: C - how to split a matrix in 4
body: <p>What`s the easiest method to split a matrix in 4?
  I have a nxn matrix, where n is multiple of 4;</p>
  
  <p><a href="https://i.stack.imgur.com/S4H2m.png" rel="nofollow noreferrer">http://i.stack.imgur.com/S4H2m.png</a></p>
  
  <p><a href="https://i.stack.imgur.com/S4H2m.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/S4H2m.png" alt="enter image description here"></a></p>
  
  <pre><code>____________________
  |        |         |
  |        |         |
  |  1st   |  2nd    |
  |        |         |
  |--------+----------
  |        |         |
  |  4th   |  3rd    |
  |        |         |
  |________|_________|
  </code></pre>
  
  <p>I don`t need to make a new matrix, only to get the ranges of i,j that refer to that new matrix;</p>