title: how many elements on list with scheme
body: <p>i need to write a function which calculates how many elements on list with scheme language.</p>
  
  <p>for example</p>
  
  <p><code>(howMany 'a)</code> returns 0<br>
  <code>(howMany '(a b))</code> returns 1<br>
  <code>(howMany '(a (b c)))</code> returns 2</p>
  
  <p>how can i do that? i did not want a working code, just only an idea for do that. so maybe you should consider to remove working codes. :) thank you</p>