import sys
from math import factorial

mod = 10**9 + 7


def Cmb(n, k):
    return factorial(n) // (factorial(n - k) * factorial(k))


n, m = list(map(int, input().split()))
a = [int(input()) for _ in range(m)]
l = len(a)

if 1 in [a[i + 1] - a[i] for i in range(l - 1)]:
    print(0)
    sys.exit()

b = [-1] + a + [n + 1]
c = []
for bi, bi2 in zip(b[:-1], b[1:]):
    c.append((bi2 - 1) - (bi + 1))  # width 2 を取れる数


def count(n):
    ret = 0
    for i in range(n // 2 + 1):
        ret += Cmb(n - i, i) % mod
    return ret


ans = 1
for ci in c:
    ans *= count(ci) % mod
    ans %= mod

print(ans)
