input: def understand_recursion():
      """ Develop a Python program to clearly understand the concept of recursion.
      >>> understand_recursion()
      Factorial of 5 is 120
      """
      def factorial(n):
          if n == 1:
              return 1
          else:
              return n * factorial(n - 1)
  
      result = factorial(5)
      print("Factorial of 5 is ", result)
output:     def factorial(n):
          if n == 1:
              return 1
          else:
              return n * factorial(n - 1)
  
      result = factorial(5)
      print("Factorial of 5 is ", result)