import sys
input = sys.stdin.readline

import math
def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

n,m = map(int,input().split())
l = [-1]+[int(input())]
for i in range(m-1):
    a = int(input())
    if a == l[-1]+1:
        print(0)
        exit()
    l.append(a)
l.append(n+1)
# print(l)

ans = 1
for i in range(m+1):
    cnt = 0
    steps = l[i+1] - l[i] -2
    for j in range(steps//2+1):
        if j == 0:
            cnt += 1
        else:
            seat = steps - j
            cnt += combinations_count(seat,j)
    ans *= cnt

print(ans % (10**9+7))