#include <stdio.h>

const int Mod = 998244353;

int main()
{
	int i, N, B[200001];
	scanf("%d", &N);
	for (i = 1; i <= N; i++) scanf("%d", &(B[i]));

	int j, k = 0, cur, prev, dp[2][2], x;
	if (B[1] == 0) {
		dp[0][0] = 1;
		dp[0][1] = 0;
	} else if (B[1] == 1) {
		dp[0][0] = 0;
		dp[0][1] = 1;
	} else {
		dp[0][0] = 1;
		dp[0][1] = 1;
	}
	for (i = 2, cur = 1, prev = 0; i <= N; i++, cur ^= 1, prev ^= 1) {
		for (x = N - i + 1; x % 2 == 0; x /= 2, k++);
		for (x = i - 1; x % 2 == 0; x /= 2, k--);
		if (k > 0) {
			if (B[i] == -1) {
				dp[cur][0] = dp[prev][0] * 2;
				if (dp[cur][0] >= Mod) dp[cur][0] -= Mod;
				dp[cur][1] = dp[prev][1] * 2;
				if (dp[cur][1] >= Mod) dp[cur][1] -= Mod;
			} else {
				dp[cur][0] = dp[prev][0];
				dp[cur][1] = dp[prev][1];
			}
		} else {
			if (B[i] == 0) {
				dp[cur][0] = dp[prev][0];
				dp[cur][1] = dp[prev][1];
			} else if (B[i] == 1) {
				dp[cur][0] = dp[prev][1];
				dp[cur][1] = dp[prev][0];
			} else {
				dp[cur][0] = dp[prev][0] + dp[prev][1];
				if (dp[cur][0] >= Mod) dp[cur][0] -= Mod;
				dp[cur][1] = dp[cur][0];
			}
		}
	}
	printf("%d\n", dp[prev][1]);
	fflush(stdout);
	return 0;
}