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




N,M = input().split()

N = int(N)
M = int(M)

a = []
ans = 1

for i in range(M):
    newa = int(input())
    a.append(newa)


for k in range(M-1):
    if (a[k+1] - a[k] == 1):
        ans = 0
            
    
    
for i in range(M + 1):
    

    if (i == 0):
        dan = a[i] - 1
    elif (i == M):
        dan = N - a[i - 1] - 1
    else:
        dan = a[i] - a[i - 1] - 2

    abletwo = (dan - (dan % 2)) // 2
    now = 0

    for j in range(abletwo + 1):

        now += cmb (dan - j , j )
        #print (dan,"dan j",j,cmb (dan - j , j ))

    ans *= now
    #print (now)

ans = ans % 1000000007
print (ans)