def combmod2(n, r):
    return (n & r) != r

def solve(n, b):
    dp = [[0] * 2 for _ in range(n + 1)]
    dp[0][0] = 1
    mod = 998244353
    for i in range(n):
        if b[i] != -1:
            if combmod2(n - 1, i):
                dp[i + 1][1] = dp[i][1]
                dp[i + 1][0] = dp[i][0]
            else:
                dp[i + 1][1] += dp[i][(1 + b[i]) % 2]
                dp[i + 1][0] += dp[i][b[i] % 2]
        else:
            if combmod2(n - 1, i):
                dp[i + 1][1] += 2 * dp[i][1]
                dp[i + 1][0] += 2 * dp[i][0]
            else:
                dp[i + 1][1] += dp[i][0] + dp[i][1]
                dp[i + 1][0] += dp[i][0] + dp[i][1]
        dp[i + 1][1] %= mod
        dp[i + 1][0] %= mod
    return dp[n][1]

n = int(input())
b = list(map(int,input().split()))
print(solve(n, b))