title: Regex to match 4 letters in a string
body: <p>I am trying to write some regex that will match a string that contains 4 or more letters in it that are not necessarily in sequence.</p>
  
  <p>The input string can have a mix of upper and lowercase letters, numbers, non-alpha chars etc, but I only want it to pass the regex test if it contains at least 4 upper or lowercase letters.</p>
  
  <p>An example of what I would like to be a valid input can be seen below:</p>
  
  <blockquote>
    <p>a124Gh0st</p>
  </blockquote>
  
  <p>I have currently written this piece of regex:</p>
  
  <pre><code>    (?(?=[a-zA-Z])([a-zA-Z])| )
  </code></pre>
  
  <p>Which returns 5 matches successfully but it will currently always pass as long as I have greater than 1 letter in the input string. if I add {4,} to the end of it then it works, but only in situations where there are 4 letters in a row.</p>
  
  <p>I am using the following website to test what I have been doing: <a href="https://regex101.com/" rel="nofollow noreferrer">regex101</a></p>
  
  <p>Any help on this would be greatly appreciated.</p>