input: Write a function to calculate the average of five numbers entered by a user. The function should take no arguments and return the calculated average. Use input() to get numbers from the user. If the input is not a number, the function should return an error message.
  assert calculate_average()==3.0 # Assuming the user enters 1, 2, 3, 4, 5
  assert calculate_average()==5.0 # Assuming the user enters 5, 5, 5, 5, 5
  assert calculate_average()==0.0 # Assuming the user enters 0, 0, 0, 0, 0
  assert calculate_average()=="Invalid input" # Assuming the user enters a non-numeric value like "a"
  assert calculate_average()=="Invalid input" # Assuming the user enters an empty string
output: def calculate_average():
      try:
          total = 0
          for i in range(5):
              num = float(input())
              total += num
          return total / 5
      except ValueError:
          return "Invalid input"