title: C get every other digit from an int
body: <p>I'm following CS50 course of Harvard University and I have to create a program in C that finds if a credit card number is valid or not.  For example, I want from this number  378282246310005 to get the every other digit like this 7224300   so I started like this:</p>
  
  <pre><code>printf("Number\n");
  long long cardNum = GetLongLong();
  </code></pre>
  
  <p>I don't know the methods I need to use to get the other digits to make my calculations.</p>