input: Write a function to calculate the average of a list of positive integers and output the result.
  
  def calculate_average(numbers):
      if not numbers:
          return 0
      total = sum(numbers)
      avg = total / len(numbers)
      return avg
  
  assert calculate_average([1, 5, 6, 7, 8]) == 5.4
  assert calculate_average([]) == 0
  assert calculate_average([10, 20, 30]) == 20.0
  assert calculate_average([5]) == 5.0
  assert calculate_average([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == 5.5
output: def calculate_average(numbers):
      if not numbers:
          return 0
      total = sum(numbers)
      avg = total / len(numbers)
      return avg