Python 计算S=1!-2!+3!-4!+5!-……n!

以下是Python计算S=1!-2!+3!-4!+5!-……n!的例子：

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)

def calculate_S(n):
    S = 0
    for i in range(1, n+1):
        if i % 2 == 0:
            S -= factorial(i)
        else:
            S += factorial(i)
    return S

n = int(input("请输入n的值："))
result = calculate_S(n)
print("计算结果为：", result)