from bisect import bisect_left
from itertools import accumulate
N, K = map(int, input().split())
a = sorted(map(int, input().split()))
b = [0]*(N+1)
ans = 1
mod = 10**9+7

for i, n in enumerate(a):
    j = bisect_left(a, K-i)
    if j > i+1:
        b[i+1] += 1
        b[j] -= 1

b = list(accumulate(b))

for i, c in enumerate(b[-2:N//2-1:-1]):
    ans = ans * max(0, (c-i)) % mod

print(ans)