input: Write a function to read in a list of 15 integers and return their sum. If the input list does not contain exactly 15 integers, raise a ValueError. Provide the function with appropriate assert tests.
  
  def sum_nums(nums):
      if len(nums) != 15:
          raise ValueError("The input list must contain exactly 15 integers.")
      total = 0
      for num in nums:
          total += num
      return total
  
  assert sum_nums([1, 5, 9, 0, 2, 4, 7, 8, 6, 10, 3, 11, 12, 13, 14])==120
  assert sum_nums([-1, -5, -9, 0, -2, -4, -7, -8, -6, -10, -3, -11, -12, -13, -14])==-105
  assert sum_nums([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0])==0
  assert sum_nums([100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500])==10500
  try:
      sum_nums([1, 2, 3, 4, 5])
      assert False, "Expected ValueError"
  except ValueError:
      pass
output: def sum_nums(nums):
      if len(nums) != 15:
          raise ValueError("The input list must contain exactly 15 integers.")
      total = 0
      for num in nums:
          total += num
      return total