#!/usr/bin/env python3

mod = 998244353
inv = (mod + 1) // 2

n = int(input())
a = list(map(int, input().split()))
dp = [0] * 5
dp[3] = 1
p = 1
pp = pow(2, max(0, n - 2), mod)
ans = 0
for i in range(n):
    nex = [0] * 5
    for j in range(5):
        k = (j - 2) * a[i] + 2
        if not (0 <= k <= 4):
            k = 2
        nex[k] = (nex[k] + dp[j]) % mod
    nex[3] = (nex[3] + p) % mod
    p = p * 2 % mod
    dp = nex
    if i < n - 1:
        ans = (ans + dp[0] * pp) % mod
    else:
        ans = (ans + dp[0]) % mod
    pp = pp * inv % mod
print(ans * pow(2, mod - n, mod) % mod)