title: Write a skip predicate
body: <p>someone asks a question about Prolog, But I even don't know what does he mean can someone explain to me??</p>
  
  <pre><code>?- Forskip([1,2,3,4,5],[3],L).
  L=[4, 5].
  ?- Forskip([c,3,6,hello,6,7,z],[6,c,a],L).
  L=[3, 6, 7, z]. 
  </code></pre>
  
  <p>can someone see the pattern and explain to me what does Forskip does???</p>