input: Write a function to demonstrate the concept of recursion by calculating the factorial of a number using a recursive function. If the given number is 0 or 1, return 1. For any other number, return the number multiplied by the factorial of the number minus 1.
  def factorial(n):
     if n == 0 or n == 1:
        return 1
     else:
        return n * factorial(n - 1)
  assert factorial(5)==120
  assert factorial(0)==1
  assert factorial(1)==1
  assert factorial(3)==6
  assert factorial(4)==24
output: def factorial(n):
     if n == 0 or n == 1:
        return 1
     else:
        return n * factorial(n - 1)