Submission #2247049

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Source Code Expand

import math,sys

def nCr(n,r):
	if n < r:
		return 0
	return int(math.factorial(n) / (math.factorial(r) * math.factorial(n-r)))

N,D = map(int,input().split())
X,Y = map(int,input().split())

if X % D != 0 or Y % D != 0:
	print(0.0)
	sys.exit()

X,Y = abs(int(X/D)), abs(int(Y/D))

if X + Y > N or (X + Y - N) % 2 == 1:
	print(0.0)
	sys.exit()

res = 0
for K in range(0 + X % 2, N + 1, 2):
	res += nCr(K, int((X + K) / 2)) *  nCr(N - K, int((Y + N - K) / 2)) * nCr(N,K)

print(res / 4**N)

Submission Info

Judge Result