题解 | 小红的双生排列

import math

n =  int(input())
#计算奇偶数的数量
if n%2 == 0:
    qishu_c = n//2
    oushu_c = n//2
else:
    qishu_c = n//2 + 1
    oushu_c = n//2
#这里答案应该是n为奇数时，阶乘一（qishu_c）乘上阶乘二 （oushu_c）；N为偶数时，乘二就可以了
#这里答案过于大，进行乘法的取模操作
M = 10**9+7
res1 = math.factorial(qishu_c)%M
res2 = math.factorial(oushu_c)%M

if n % 2 == 0:
    res = res1 * res2 % M
    print((res*2)%M)
else:
    res = res1 * res2 % M
    print(res)