Why isn't my carousel sliding?

Hi, I’m trying to figure out carousels from the tutorial on ws3schools using Bootstrap 3. However, the carousel in this pen won’t slide and I can’t see where I’ve messed up. If someone could point out what I’ve done wrong I would appreciate it greatly because I can’t see it for the life of me.

Thanks

add these:

  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>

Ah, thank you very much, this was driving me mad!