title: Get Post number(digits) In a String
body: <p>How to find the digit(post number) after @ and before ;; since there are other digits in the string. Finally, it produced [507, 19, 1].</p>
  
  <p>Example:</p>
  
  <pre><code>   post507 = "@507::empty in Q1/Q2::can list be empty::yes"
     post19 = "@19::Allowable functions::empty?, first, rest::"
     post1 = "@1::CS116 W2015::Welcome to first post::Thanks!"
     cs116 =   [post507, post1, post19]
  
  
     print (search_piazza(cs116, "l")) =&gt;[507,1,19]
  </code></pre>