N = int(input())
As = list(map(int, input().split()))

MOD = 998244353

half = pow(2, MOD - 2, MOD)

alphas = [0] * 5
dp = [0] * (N + 1)
dpsum = 0
prod = 1
for i, A in enumerate(As):
    prod *= A
    if not (-2 <= prod <= 2):
        prod = 0
    if prod == -2:
        dp[i + 1] += pow(2, MOD - 2 - i, MOD)
    alphas[1] += 1
    new_alphas = [0] * 5
    for j in range(-2, 3):
        index = j * A
        if not (-2 <= index <= 2):
            index = 0
        new_alphas[index] += alphas[j] * half
        new_alphas[index] %= MOD
    alphas = new_alphas
    dp[i + 1] += (dpsum + alphas[-2]) % MOD
    dp[i + 1] %= MOD
    dpsum += dp[i + 1]
    dpsum = dpsum * half % MOD
    
# print(dp)

print(dp[-1])