input: Write a python function special_factorial to calculate the combined factorial product of a given integer. The combined factorial is defined as: combined_factorial(n) = n! * (n-1)! * (n-2)! * ... * 1! where n > 0. The function should take an integer as input and return the combined factorial of this integer.
  assert special_factorial(4) == 288
  assert special_factorial(5) == 34560
  assert special_factorial(7) == 125411328000
  assert special_factorial(1) == 1
output: def special_factorial(n):
      def factorial(x):
          if x == 0 or x == 1:
              return 1
          else:
              return x * factorial(x - 1)
      result = 1
      for i in range(1, n + 1):
          result *= factorial(i)
      return result