jQuery IF statement only works on the first instance

I have an IF statement very similar to this Fiddle here:

http://ift.tt/1nxk5hE

What I'm wanting to know is, how do I display the alert() only once ALL divs with the .ccn class have a value over 1000, not just the first instance. I have tried the each() function but I'm not too sure how to use it.

$(".ccn").keyup(function() {
  if ($(".ccn").val() >= 1000)
    alert('test');
});

<div class="cardNumber">
  <input type="text" value="" maxlength="4" name="ccn" class="ccn">
  <input type="text" value="" maxlength="4" name="ccn" class="ccn">
  <input type="text" value="" maxlength="4" name="ccn" class="ccn">
  <input type="text" value="" maxlength="4" name="ccn" class="ccn">
</div>

<ul>
  <li class="checkNumber">Card Number</li>
</ul>