input: Write a function to find the smallest number in a list.
  assert find_smallest([4, 2, 7, 1, 9, 3]) == 1
  assert find_smallest([10, 20, 5, 3, 8]) == 3
  assert find_smallest([-3, -1, -7, -2]) == -7
output: def find_smallest(lst):
      return min(lst)