from functools import lru_cache

N, M = map(int, input().split())
a = list(int(input()) for _ in range(M))

MOD = pow(10, 9) + 7

isOk = True
for i in range(M-1):
    if a[i] + 1 == a[i+1]:
        isOk = False
    
@lru_cache(maxsize = None)
def func(n):
    if n <= 0:
        return 1
    cnt = 0
    if n >= 2:
        cnt += func(n-2) % MOD
    if n >= 1:
        cnt += func(n-1) % MOD
    return cnt

if not isOk:
    print(0)
else:
    ans = 1
    s = 0
    for i in range(M+1):
        if i >= M:
            e = N
        else:
            e = a[i] - 1

        ans = ans * func(e-s) % MOD

        if i >= M:
            break

        s = a[i] + 1

    print(ans)
