15439

N = int(input())

if N == 1:
	print(0)
else:
	print(N*(N - 1))

24723

N = int(input())
print(2 ** N)

10872

N = int(input())
res = 1

for i in range(1, N+1):

	res *= i

print(res)

11050

일부러 combination 안 썼음

N, K = map(int, input().split())

def fac(num):

res = 1

for i in range(1, num+1):

	res *= i

return res

N_f = fac(N)
K_f = fac(K)
NK_f = fac(N-K)

print(N_f // (K_f*NK_f))

# 1010

def fac(num):
res = 1
for i in range(1, num + 1):
res *= i
return res

T = int(input())

for _ in range(T):
N, M = map(int, input().split())
M_f = fac(M)
N_f = fac(N)
MN_f = fac(M - N)
print(M_f // (N_f * MN_f))