N,M =map(int,input().split())
if M>0:
    a = [0]*M
    for i in range(M):
        a[i] = int(input())

ans = int(1)

A = [0]*(M+1)
A[0]=N
if M!=0:
    A[0] = a[0] - 1
    A[M] = N - a[M-1]-1
    for i in range(M-1):
        A[i+1] = a[i+1] - a[i]- 2
        if A[i+1]==-1:
            ans = 0


SA =[0]*N
SA[0] = int(1)
SA[1] = int(1)
if N>2:
    for i in range(N - 1):
        SA[i + 2] = SA[i + 1] + SA[i]
        SA[i + 2] = SA[i + 2] % 1000000007

for i in range(M+1):
    if A[i]>=0:
        ans *= SA[A[i]]
        ans = ans%1000000007


print(ans)
