import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")
import bisect

def getlist():
	return list(map(int, input().split()))

def inverse(N, mod):
	return (pow(N, mod - 2, mod))

#処理内容
def main():
	N, K = getlist()
	n = int(N // 2)
	A = list(sorted(getlist()))
	ans = 1
	stop = None
	for i in range(n):
		ind = N - 1 - i
		ind2 = bisect.bisect_left(A, K - A[ind] + 1) - 1
		if ind2 < ind:
			if ind2 + 1 - i > 0:
				ans = (ans * (ind2 + 1 - i)) % con
			else:
				ans = 0
				stop = INF
				break
		else:
			stop = n - i
			break

	if stop == INF:
		print(0)
		return
	elif stop == None:
		print(ans)
		return

	for i in range(1, 2 * stop + 1):
		ans *= i
		ans %= con

	inv_2 = inverse(2, con)
	for i in range(stop):
		ans *= inv_2
		ans %= con

	for i in range(1, stop + 1):
		ans *= inverse(i, con)
		ans %= con

	print(ans)


if __name__ == '__main__':
	main()