mod = 998244353
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

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

    half = pow(2, mod-2, mod)
    dp = [[0] * 5 for _ in range(N)]
    dp[0][1] = 1
    ans = 0
    for i, a in enumerate(A[:-1]):
        dp[i+1][1] = half
        for j in range(-2, 3):
            ja = j * a
            if not -2 <= ja <= 2:
                ja = 0
            dp[i+1][ja] = (dp[i+1][ja] + dp[i][j] * half)%mod
            if ja == -2:
                ans = (ans + dp[i][j] * half)%mod
    for j in range(-2, 3):
        if j * A[-1] == -2:
            ans = (ans + dp[-1][j])%mod
    print(ans)


if __name__ == '__main__':
    main()