n, m = map(int, input().split())
MOD = 1000000007

fact=[0,1]
fact_inv=[0]*(n+1)
for i in range(2,n+1):
  fact.append(fact[-1]*i % MOD)

fact_inv[n] = pow(fact[n],MOD-2,MOD)
for i in range(n-1,-1,-1):
  fact_inv[i] = fact_inv[i+1]*(i+1)%MOD

def comb(n,r):
  return fact[n]*fact_inv[r]*fact_inv[n-r]%MOD

def sigmaComb(dis):
  ans=0
  if dis == 1 or dis == 0:
    return 1
  end=dis//2 if dis%2 != 0 else dis//2+1
  for i in range(end):
    t=comb(dis-i,i)
    ans+=t
  return ans

hole=[0]
ans=1
for i in range(m):
  t = int(input())
  availLeft=hole[-1]
  availRight=t-1
  dis=availRight-availLeft
  if dis <0:
    ans=0
    break

  ans=ans*sigmaComb(dis)%MOD
  # print("dis=",dis,t,ans)
  hole.append(t+1)
else:
  availLeft=hole[-1]
  availRight=n
  dis=availRight-availLeft
  #print("dis=",dis,hole[-1],ans)
  ans=ans*sigmaComb(dis)%MOD

print(ans%MOD)