import sys
input = sys.stdin.readline
N = int(input())
a = list(map(int, input().split()))
mod = 998244353

def combi(n, k):
  if n < k: return 0
  if n == k: return 1
  if n > k: return 1

def lucas(n, k):
  res = 1
  while n and k:
    if n & 1 < k & 1: res = 0
    elif n & 1 == 0: res &= 1
    else: res &= combi(n & 1, k & 1)
    n >>= 1
    k >>= 1
  return res
dp = [0] * 2
dp[0] = 1
for i in range(N):
  c = lucas(N - 1, i)
  #print(c)
  if a[i] == 1:
    if c: dp[0], dp[1] = dp[1], dp[0]
  if a[i] == -1:
    if c == 0: dp[0], dp[1] = dp[0] * 2 % mod, dp[1] * 2 % mod
    else: dp[0], dp[1] = (dp[0] + dp[1]) % mod, (dp[0] + dp[1]) % mod
print(dp[-1])