input: Write a function to calculate the average of five numbers entered by a user. The function should accept a list of five integers and return the average value as a float.
  
  assert calculate_average([1, 2, 3, 4, 5])==3.0
  assert calculate_average([10, 20, 30, 40, 50])==30.0
  assert calculate_average([0, 0, 0, 0, 0])==0.0
  assert calculate_average([-5, -4, -3, -2, -1])==-3.0
  assert calculate_average([15, 25, 35, 45, 55])==35.0
output: def calculate_average(numbers):
      return sum(numbers) / len(numbers)