n,m = map(int,input().split(" "))
a=[]
ans = 1
for i in range(m):
    a.append(int(input()))
    if a[i]-1 == a[i-1]:
        ans = 0
if ans == 1:
    for j in range(n,-1,-1):
        if j in a:
            ans *= 1
        elif j+1 in a or j+2 in a:
            ans *= 1
        elif j+2 > n:
            ans *= 1
        elif not(j+3 in a) and not(j+3 > n):
            temp = ans
            ans += t
            t = temp
        else:
            t = ans
            ans *= 2

print(ans % 1000000007)
