input: Write a function to calculate the cube of a given integer. The function should prompt the user for an integer input, compute its cube, and print the result.
  assert cube_of_number(3) == 27
  assert cube_of_number(-2) == -8
  assert cube_of_number(0) == 0
  assert cube_of_number(5) == 125
  assert cube_of_number(-1) == -1
output: def cube_of_number(n):
      return n ** 3