import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.math.BigInteger;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());
		String[] sa = br.readLine().split(" ");
		int[] b = new int[n];
		for (int i = 0; i < n; i++) {
			b[i] = Integer.parseInt(sa[i]);
		}
		br.close();

		int mod = 998244353;
		Kaijou kai = new Kaijou(n, mod);
		Kaijou2 kai2 = new Kaijou2(n, 2);

		int n1 = n - 1;
		int a = 0;
		int x = 0;
		int y = 0;
		for (int i = 0; i < n; i++) {
			long v = kai2.comb(n1, i);
			if (v % 2 == 1) {
				if (b[i] == 1) {
					a++;
				} else if (b[i] == -1) {
					x++;
				}
			}
			if (b[i] == -1) {
				y++;
			}
		}

		long ans = 0;
		if (a % 2 == 0) {
			for (int i = 1; i <= x; i += 2) {
				ans += kai.comb(x, i);
			}
		} else {
			for (int i = 0; i <= x; i += 2) {
				ans += kai.comb(x, i);
			}
		}
		ans %= mod;
		ans *= power(2, y - x, mod);
		ans %= mod;
		System.out.println(ans);
	}

	static long power(long x, long n, int m) {
		if (n == 0) {
			return 1;
		}
		long val = power(x, n / 2, m);
		val = val * val % m;
		if (n % 2 == 1) {
			val = val * x % m;
		}
		return val;
	}

	static class Kaijou {
		long[] p, pi;
		int m;

		public Kaijou(int n, int mod) {
			n++;
			m = mod;
			p = new long[n];
			pi = new long[n];
			p[0] = 1;
			pi[0] = 1;
			for (int i = 1; i < n; i++) {
				p[i] = p[i - 1] * i % m;
			}
			pi[n - 1] = BigInteger.valueOf(p[n - 1])
					.modInverse(BigInteger.valueOf(m)).longValue();
			for (int i = n - 1; i > 1; i--) {
				pi[i - 1] = pi[i] * i % m;
			}
		}

		public long comb(int n, int r) {
			if (n < r) return 0;
			return p[n] * pi[r] % m * pi[n - r] % m;
		}

		public long perm(int n, int r) {
			if (n < r) return 0;
			return p[n] * pi[n - r] % m;
		}
	}

	static class Kaijou2 {
		long[] p, pi;
		int[] im, cm;
		int m;

		public Kaijou2(int n, int mod) {
			n++;
			m = mod;
			p = new long[n];
			pi = new long[n];
			im = new int[n];
			cm = new int[n];
			p[0] = 1;
			pi[0] = 1;
			for (int i = 1; i < n; i++) {
				int i2 = i;
				while (i2 % m == 0) {
					cm[i]++;
					i2 /= m;
				}
				p[i] = p[i - 1] * i2 % m;
				im[i] = i2;
				cm[i] += cm[i - 1];
			}
			pi[n - 1] = BigInteger.valueOf(p[n - 1])
					.modInverse(BigInteger.valueOf(m)).longValue();
			for (int i = n - 1; i > 1; i--) {
				pi[i - 1] = pi[i] * im[i] % m;
			}
		}

		public long comb(int n, int r) {
			if (n < r) return 0;
			if (cm[n] > cm[r] + cm[n - r]) {
				return 0;
			}
			return p[n] * pi[r] % m * pi[n - r] % m;
		}

		public long perm(int n, int r) {
			if (n < r) return 0;
			if (cm[n] > cm[n - r]) {
				return 0;
			}
			return p[n] * pi[n - r] % m;
		}
	}
}