input: Write a python function to find the smallest number in an array.
  assert find_smallest([3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]) == 1
  assert find_smallest([10, 20, 5, 40, 30]) == 5
  assert find_smallest([-1, -5, -3, -4, -2]) == -5
output: def find_smallest(arr):
      return min(arr)