import math
import sys

n, m = map(int, input().split())
a_list = [-1]
for _ in range(m):
    a_list.append(int(input()))
a_list.append(n + 1)

fact_memo = dict()
def fact(n):
    if n in fact_memo.keys():
        return fact_memo[n]
    f = math.factorial(n)
    fact_memo[n] = f
    return f

memo = dict()
ans = 1
cur = a_list[0]
for i, a in enumerate(a_list):
    if i == 0:
        continue
    sub = a - cur - 1
    cur = a
    if sub <= 2:
        if sub == 0:
            print(0)
            sys.exit()
        continue
    sub -= 1
    if sub in memo.keys():
        ans *= memo[sub]
        continue
    count = 0
    for j in range(sub // 2 + 1):
        count += fact(sub - j) // fact(j) // fact(sub - j * 2)
    memo[sub] = count
    ans *= count
print(ans % 1000000007)
