import sys

mod = 10**9 + 7


def extgcd(a, b):
    r = [1, 0, a]
    w = [0, 1, b]
    while w[2] != 1:
        q = r[2] // w[2]
        r2 = w
        w2 = [r[0] - q * w[0], r[1] - q * w[1], r[2] - q * w[2]]
        r = r2
        w = w2
    return [w[0], w[1]]


def mod_inv(a, m):
    x = extgcd(a, m)[0]
    return (m + x % m) % m


def Cmb(n, k):
    res = 1
    for i in range(1, n + 1):
        res = res * i % mod
    for i in range(1, k + 1):
        res = res * mod_inv(i, mod) % mod
    for i in range(1, n - k + 1):
        res = res * mod_inv(i, mod) % mod
    return res


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)
