def cmb(n, r):
    if n - r < r: r = n - r
    if r == 0: return 1
    if r == 1: return n

    numerator = [n - r + k + 1 for k in range(r)]
    denominator = [k + 1 for k in range(r)]

    for p in range(2,r+1):
        pivot = denominator[p - 1]
        if pivot > 1:
            offset = (n - r) % p
            for k in range(p-1,r,p):
                numerator[k - offset] /= pivot
                denominator[k] /= pivot

    result = 1
    for k in range(r):
        if numerator[k] > 1:
            result *= int(numerator[k])

    return result

def sumcmb(T):
    count=0
    m=T
    while m>=0:
        count+=cmb(T,m)
        T-=1
        m-=2
    return(count)


N,M=map(int,input().split())
A=[int(input()) for i in range(M)]
mod=10**9+7
for i in range(M-1):
    if A[i]+1==A[i+1]:
        print(0)
        exit()

if 1 not in A:
    A.insert(0,-1)
if N not in A:
    A.append(N+1)


count=1
for i in range(len(A)-1):
    T=max(A[i+1]-1 - (A[i]+1),1)
    #print(sumcmb(T))
    count*=sumcmb(T)
    count%=mod
print(count)
