input: Write a function to find the smallest number in a list.
  assert smallestNumber([4, 5, 6, 7, 8]) == 4
  assert smallestNumber([10, 3, 5, 7, 2, 15]) == 2
  assert smallestNumber([99, 23, 1, 45, 0, -5]) == -5
output: def smallestNumber(lst):
      return min(lst)