title: Error: This expression has type int but an expression was expected of type 'a option
body: <p>Here is my code:</p>
  
  <pre><code>let rec size = function 
      | [] -&gt; 0
      | t::q -&gt; 1 + size q
  
  let rec n k v lst = match lst with 
      | [] -&gt; None 
      | t::q when (v - size q) = k -&gt; t
      | _::q -&gt; n k v q
  
  let () = print_int (n (3) (5) ([ 1 ; 2; 3; 4; 5 ]) )
  </code></pre>
  
  <p>It's saying the following:</p>
  
  <pre><code>File "main.ml", line 10, characters 33-34:
  Error: This expression has type int but an expression was expected of type
           'a option
  </code></pre>
  
  <p>I don't understand what it means. 
  I am trying to print the nth element of a list. I mean <code>print_int</code> is waiting for an <code>int</code> and <code>k</code>, <code>v</code> are integers.</p>