def comb(n, r, mod):
    if ( r<0 or r>n ):
        return 0
    r = min(r, n-r)
    return g1[n] * g2[r] * g2[n-r] % mod

mod = 10**9+7 #出力の制限
N = 10**4
g1 = [1, 1] # 元テーブル
g2 = [1, 1] #逆元テーブル
inverse = [0, 1] #逆元テーブル計算用テーブル

for i in range( 2, N + 1 ):
    g1.append( ( g1[-1] * i ) % mod )
    inverse.append( ( -inverse[mod % i] * (mod//i) ) % mod )
    g2.append( (g2[-1] * inverse[-1]) % mod )

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 comb(n - 1, i, 2):
                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 comb(n - 1, i, 2):
                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))