title: Prolog find GCD of a list of numbers
body: <p>Hello I am trying to find the GCD of a list of numbers in Prolog, but I cannot manage to do it.
  Could you please help?</p>
  
  <p>I am not even barely close so I wont share any of my work till now.
  PP: In the process of trying to solve this I've encountered another problem that I can't solve, if you can help with this one too I will be grateful. It's finding all the common divisors of two numbers.</p>
  
  <p>Thanks!</p>