input: Write a python function to rotate a list by n elements to the left.
  assert rotateList([1, 2, 3, 4, 5, 6], 3) == [4, 5, 6, 1, 2, 3]
  assert rotateList([1, 2, 3, 4, 5], 2) == [3, 4, 5, 1, 2]
  assert rotateList([1, 2, 3], 1) == [2, 3, 1]
output: def rotateList(lst, n):
      n = n % len(lst)
      return lst[n:] + lst[:n]