# -*- coding: utf-8 -*-

from operator import mul
from functools import reduce

N, M = map(int, input().split())
a = [int(input()) for x in range(M)]


def cmb(n, r):
    if n - r < r: r = n - r
    if r == 0: return 1
    if r == 1: return n

    numerator = [n - r + k + 1 for k in range(r)]
    denominator = [k + 1 for k in range(r)]

    for p in range(2,r+1):
        pivot = denominator[p - 1]
        if pivot > 1:
            offset = (n - r) % p
            for k in range(p-1,r,p):
                numerator[k - offset] /= pivot
                denominator[k] /= pivot

    result = 1
    for k in range(r):
        if numerator[k] > 1:
            result *= int(numerator[k])

    return result

def calc_routes(dan):
    tmp = 1
    for i in range(int(dan/2)):
        i += 1
        n = dan - i
        # tmp += factorial(n) / factorial(i) / factorial(n - i)
        tmp += cmb(n, i)

    return tmp

routes = 1
prev = 0
for x in a:
    if x == prev:
        routes = 0
        break
    else:
        dan = (x-1) - prev
        routes = (routes * calc_routes(dan)) % 1000000007
        prev = x+1

routes = (routes * calc_routes(N-prev)) % 1000000007
print(int(routes))