input: Write a function to calculate the factorial of a given integer and print the result. The function should use recursion to compute the factorial. If the input number is less than or equal to 1, return 1. Otherwise, return the product of the number and the factorial of the number minus one.
  
  def factorial(num):
      if num <= 1:
          return 1
      else:
          return num * factorial(num - 1)
  
  assert factorial(7)==5040
  assert factorial(0)==1
  assert factorial(1)==1
  assert factorial(5)==120
  assert factorial(10)==3628800
output: def factorial(num):
      if num <= 1:
          return 1
      else:
          return num * factorial(num - 1)