title: How to get a substring of char out of a string of ints
body: <p>I want to return the substring of alpha characters between two sets of ints of any length.  </p>
  
  <p>For example, with the strings below, I would like to return the substring "JKL":</p>
  
  <pre><code>123JKL1234
  456545645456JKL13
  </code></pre>