package contest200925;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;

public class D {
	InputStream is;
	PrintWriter out;
	String INPUT = "";
	int mod = 998244353;
	long i2 = invl(2, mod);
	
	void solve()
	{
		int n = ni();
		int[] a = na(n);
		Datum L = pm(a);
		Datum R = pm(rev(a));
		long ans = 0;

		// 5/4*1+1+1

		// L, R
		// 2^-(L+1+R+1)
		for(int i = 0;i < n;i++){
			if(a[i] == 2){
				ans += L.wp[i] * R.wm[n-1-i];
				ans += L.wm[i] * R.wp[n-1-i];
			}else if(a[i] == -2){
				ans += L.wp[i] * R.wp[n-1-i];
				ans += L.wm[i] * R.wm[n-1-i];
			}
			ans %= mod;
		}
		out.println(ans*i2%mod*i2%mod);
	}

	public static int[] rev(int[] a){int[] b = new int[a.length];for(int i = 0;i < a.length;i++)b[a.length-1-i] = a[i];return b;}


	Datum pm(int[] a)
	{
		int n = a.length;
		int[] lp = new int[n];
		int[] lm = new int[n];
		long[] wp = new long[n];
		long[] wm = new long[n];
		lp[0] = 1;
		wp[0] = 2;
		for(int i = 0;i < n;i++){
			if(i < n-1) {
				if (Math.abs(a[i]) == 2 || Math.abs(a[i]) == 0) {
					lp[i + 1] = 1;
					lm[i + 1] = 0;
					wp[i+1] = 1;
					wm[i+1] = 0;
				}else if(a[i] == 1){
					lp[i+1] = lp[i] + 1;
					lm[i+1] = lm[i];
					wp[i+1] = (wp[i] * i2 + 1) % mod;
					wm[i+1] = wm[i] * i2 % mod;
				}else{
					lp[i+1] = lm[i] + 1;
					lm[i+1] = lp[i];
					wp[i+1] = (wm[i] * i2 + 1) % mod;
					wm[i+1] = wp[i] * i2 % mod;
				}
			}
		}
		return new Datum(lp, lm, wp, wm);
	}

	static class Datum
	{
		int[] lp, lm;
		long[] wp, wm;

		public Datum(int[] lp, int[] lm, long[] wp, long[] wm) {
			this.lp = lp;
			this.lm = lm;
			this.wp = wp;
			this.wm = wm;
		}
	}

	public static long invl(long a, long mod) {
		long b = mod;
		long p = 1, q = 0;
		while (b > 0) {
			long c = a / b;
			long d;
			d = a;
			a = b;
			b = d % b;
			d = p;
			p = q;
			q = d - c * q;
		}
		return p < 0 ? p + mod : p;
	}


	void run() throws Exception
	{
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//		Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){
//			@Override
//			public void run() {
//				long s = System.currentTimeMillis();
//				solve();
//				out.flush();
//				if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//			}
//		};
//		t.start();
//		t.join();
	}
	
	public static void main(String[] args) throws Exception { new D().run(); }
	
	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	
	private int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private double nd() { return Double.parseDouble(ns()); }
	private char nc() { return (char)skip(); }
	
	private String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private long[] nal(int n)
	{
		long[] a = new long[n];
		for(int i = 0;i < n;i++)a[i] = nl();
		return a;
	}
	
	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private int[][] nmi(int n, int m) {
		int[][] map = new int[n][];
		for(int i = 0;i < n;i++)map[i] = na(m);
		return map;
	}
	
	private int ni() { return (int)nl(); }
	
	private long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); }
}