m = map(int, (input().split()))
a = {int(input()) for i in range(m)}
mod = 10 ** 9 + 7
 
x = 1 if 1 not in a else 0
dp = [1, x] + [0] * (n - 1)
 
for i in range(2, n + 1):
    if i in a:
        continue
    dp[i] = (dp[i - 1] + dp[i - 2])
 
print(dp[-1] % mod)