input: def understand_recursion():
      """ This program is to understand recursion in Python.
      It defines a recursive function to calculate the factorial of a number.
      >>> result = factorial(5)
      >>> print("Factorial of 5 is ", result)
      Factorial of 5 is 120
      """
  
  def factorial(n):
     if n == 1:
        return 1
     else:
        return n * factorial(n - 1)
output:     result = factorial(5)
      print("Factorial of 5 is ", result)