title: Update max value to -1 in 2D array
body: <p>I have a 2D array:</p>
  
  <pre><code>L = array([[ 4,  5,  3, 10,  1],
             [10,  1, 10, 10,  5],
             [ 1,  6,  3,  2,  7],
             [ 5,  1,  1,  5,  1],
             [ 8,  8,  8, 10,  5]])
  </code></pre>
  
  <p>I need to change maximum value to -1. Result array will be like below:</p>
  
  <pre><code>R = array([[ 4,  5,  3, -1,  1],
             [-1,  1, -1, -1,  5],
             [ 1,  6,  3,  2,  7],
             [ 5,  1,  1,  5,  1],
             [ 8,  8,  8, -1,  5]])
  </code></pre>
  
  <p>My array L will be a random 5*5 size array.. How can i do this?</p>