input: Write a function to compute the factorial of a given integer. The function should take an integer as input and return its factorial. If the input integer is less than or equal to 1, the function should return 1.
  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(3) == 6
output: def factorial(num):
      if num <= 1:
          return 1
      else:
          return num * factorial(num - 1)