Calculate Alternating Factorial Series in Python

def main():
	"""
	Prints the sum of a series.
	"""

	n = int(input("Enter n: "))
	s = series(n)
	print(s)


def series(n: int):
	"""
	Calculates the sum of the series: 0! - 1! + 2! - 3! + ... ± n.
	"""

	# Initialize the values with 0!
	ith_factorial = 1
	series_sum = 1
	sign = -1

	# Calculate the sum from 1!...n
	for i in range(1, n + 1):
		ith_factorial *= i
		series_sum += sign * ith_factorial
		sign *= -1

	return series_sum


if __name__ == "__main__":
	main()