def fiv(n):
    return (((1+(5)**(1/2))/2)** (n + 1) - ((1-(5)**(1/2))/2)** (n + 1))/(5**(1/2))

n, m = map(int, input().split())
broken = [input() for i in range(m)]

p = [0] * (m + 1) #broken間の登り方list

for i in range(m + 1):
    if i == 0: #a1 さいしょ
        if broken[0] == 1:
            p[0] = 1
        else:
            p[0] = fiv(broken[0] -1)
    if i == m: #am さいご
        if broken[m] == n - 1:
            p[m] = 1
        else:
            p[m] = fiv(n - broken[0] - 1)
    
    else:
        if broken[i] - broken[i - 1] - 1 == 0:
            print('0')
            exit()
        else:
            p[i] = fiv(broken[i] - broken[i - 1] - 1)

ans = 1
for i in range(m + 1):
    ans = ans * p[i]

print(ans)