title: Need regular expression for this string
body: <p>I am writing a small program to do some calculations.</p>
  
  <p>Basically the input is the following: </p>
  
  <pre><code>-91 10 -4 5
  </code></pre>
  
  <p>The digits can have the negative sign or not. They are also separated by a space. 
  I need a regular expression  to filter each digit including the sign if there is one. </p>
  
  <p>Thanks!</p>
  
  <p>Adam</p>