n = int(input())
s = 0
for i in range(1, n + 1):
    t = 1
    for j in range(1, i + 1):
        t = t * j
    if i % 2 == 1:
        s = s + t
    else:
        s = s - t
print(s)

/**************************************************************
	Problem: 1518
	User: admin
	Language: Python
	Result: Accepted
	Time:171 ms
	Memory:34480 kb
****************************************************************/