input: Write a function to find the maximum element in an array.
  assert maxElement([1, 2, 3, 4, 5]) == 5
  assert maxElement([10, 20, 30, 40, 50]) == 50
  assert maxElement([-1, -2, -3, -4, -5]) == -1
output: def maxElement(arr):
      return max(arr)