input: Write a python function to find the kth smallest element in an array.
  assert kth_smallest([7, 10, 4, 3, 20, 15], 3) == 7
  assert kth_smallest([7, 10, 4, 3, 20, 15], 4) == 10
  assert kth_smallest([12, 3, 5, 7, 19], 2) == 5
  assert kth_smallest([1, 23, 12, 9, 30, 2, 50], 5) == 23
output: def kth_smallest(arr, k):
      arr.sort()
      return arr[k-1]