
"""simple docstring"""
def     __lowerCamelCase  (		UpperCamelCase__      ):


	"""simple docstring"""






	if not isinstance(UpperCamelCase__				,     UpperCamelCase__      ):
		raise ValueError("double_factorial() only accepts integral values"      )
	if n < 0:
		raise ValueError("double_factorial() not defined for negative values"      )
	return 1 if n <= 1 else n * double_factorial(n - 2      )


if __name__ == "__main__":
			import doctest

			doctest.testmod()






"""simple docstring"""
def     __lowerCamelCase  (		UpperCamelCase__ = 400_0000      ):


	"""simple docstring"""






	_UpperCAmelCase =						1
	_UpperCAmelCase =						2
	_UpperCAmelCase =						0
	while j <= n:
		if j % 2 == 0:
			total += j
		_UpperCAmelCase ,      _UpperCAmelCase =						j, i + j

	return total


if __name__ == "__main__":
			print(f'''{solution() = }''')




