id = 120
group = 'lists'
number = 27
visible = True
facts = None

solution = '''\
count(_, [], 0).
count(X, [X|T], N) :-
  count(X, T, NT),
  N is NT + 1.
count(X, [Y|T], NT) :-
  X \== Y,
  count(X, T, NT).
'''