input: Write a function called calculate_cube that takes an integer as input and returns its cube. If the input is not an integer, the function should return "Invalid input". Add the following assert tests to ensure the function works correctly:
  assert calculate_cube(3) == 27
  assert calculate_cube(0) == 0
  assert calculate_cube(-2) == -8
  assert calculate_cube("five") == "Invalid input"
output: def calculate_cube(n):
      if isinstance(n, int):
          return n ** 3
      else:
          return "Invalid input"