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

ans = int(1)

A = [0]*(M+1)
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
        print(ans)
        exit()

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

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


print(int(ans))
