using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var b = NList;
        var ncr = new NCR(n - 1, 2);
        var dp0 = 1L;
        var dp1 = 0L;
        var mod = 998_244_353;
        for (var i = 0; i < b.Length; ++i)
        {
            var ev = NcrIsEven(n - 1, i);
            var ndp0 = 0L;
            var ndp1 = 0L;
            if (b[i] != 1)
            {
                ndp0 = (ndp0 + dp0) % mod;
                ndp1 = (ndp1 + dp1) % mod;
            }
            if (b[i] != 0)
            {
                if (ev)
                {
                    ndp0 = (ndp0 + dp0) % mod;
                    ndp1 = (ndp1 + dp1) % mod;
                }
                else
                {
                    ndp0 = (ndp0 + dp1) % mod;
                    ndp1 = (ndp1 + dp0) % mod;
                }
            }
            dp0 = ndp0;
            dp1 = ndp1;
        }
        WriteLine(dp1);
    }
    static bool NcrIsEven(int n, int r)
    {
        return DCount(n) - DCount(r) - DCount(n - r) > 0;
    }
    static int DCount(int n)
    {
        var ans = 0;
        for (var i = 2; i <= n; i <<= 1)
        {
            ans += n / i;
        }
        return ans;
    }
    class NCR
    {
        int[] facts;
        int[] revFacts;
        int mod;
        public NCR(int n, int mod)
        {
            facts = new int[n + 1];
            revFacts = new int[n + 1];
            this.mod = mod;
            facts[0] = 1;
            var tmp = 1L;
            for (var i = 1; i <= n; ++i)
            {
                tmp = tmp * i % mod;
                facts[i] = (int)tmp;
            }
            tmp = Exp(facts[n], mod - 2);
            revFacts[n] = (int)tmp;
            for (var i = n; i > 1; --i)
            {
                tmp = tmp * i % mod;
                revFacts[i - 1] = (int)tmp;
            }
            revFacts[0] = 1;
        }
        public long Exp(long n, long k)
        {
            n = n % mod;
            if (k == 0) return 1;
            if (k == 1) return n;
            var half = Exp(n, k / 2);
            var result = half * half % mod;
            return ((k % 2) == 0) ? result : (result * n % mod);
        }
        public long Calc(int n, int r)
        {
            return (long)facts[n] * revFacts[r] % mod * revFacts[n - r] % mod;
        }
        /// <summary>nが大きくrが小さい場合の計算</summary>
        public long Calc2(int n, int r)
        {
            var tmp = 1L;
            for (var i = 0; i < r; ++i)
            {
                tmp = tmp * (n - i) % mod;
            }
            return tmp * revFacts[r] % mod;
        }
        public long NPR(int n, int r)
        {
            return (long)facts[n] * revFacts[r] % mod;
        }
        public long Fact(int n)
        {
            return facts[n];
        }
        public long RevFact(int n)
        {
            return revFacts[n];
        }
        public long Inverse(int n)
        {
            return (long)revFacts[n] * facts[n - 1] % mod;
        }
    }
}