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

N, M = map(int, input().split())

sl = []
cnt = -1
for i in range(M):
    a = int(input())
    b = (a - 1) - (cnt + 1)
    if b == -1:
        print(0)
        break
    sl.append(max(b, 1))
    cnt = a
else:
    sl.append(max(N - (a + 1), 1))
    ans = 1
    for s in sl:
        p = 0
        for i in range(s):
            j = s - i
            if (i <= j):
                p += combinations_count(j, i)
            else:
                break
        ans *= p
        ans = ans % 1000000007
    print(ans % 1000000007)