input: Write a function to calculate the average of five numbers entered by the user. The function should prompt the user to input five numbers, calculate their average, and then print the result. If no numbers are entered, the function should return 0.
  assert calculate_average([1, 2, 3, 4, 5])==3.0
  assert calculate_average([0, 0, 0, 0, 0])==0.0
  assert calculate_average([-1, -2, -3, -4, -5])==-3.0
  assert calculate_average([])==0
output: def calculate_average(numbers):
      if not numbers:
          return 0
      return sum(numbers) / len(numbers)