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

class comb():
  F = [1, 1]
  Fi = [1, 1]
  I = [0, 1]
  def __init__(self, num, mod):
    self.MOD = mod
    for i in range(2, num + 1):
      self.F.append((self.F[-1] * i) % mod)
      self.I.append(mod - self.I[mod % i] * (mod // i) % mod)
      self.Fi.append(self.Fi[-1] * self.I[i] % mod)
  def com(self, n, k):
    if n < k: return 0
    if n < 0 or k < 0: return 0
    return self.F[n] * (self.Fi[k] * self.Fi[n - k] % self.MOD) % self.MOD


MOD = 10 ** 9 + 7

for i in range(1, M):
  if a[i] - a[i - 1] == 1:
    print(0)
    exit()

com = comb(N, MOD)
ans = 1
x = 0
a = a + [N + 1]

for i in a:
  t = i - 1 - x
  at = 0
  for j in range(t // 2 + 1):
    k = t - j
    at = at + com.com(k, j) % MOD
  ans = ans * at % MODs
  x = i + 1
  

print(ans)