Problem:
Score : 700 points

Problem Statement

Takahashi has a tower which is divided into N layers.
Initially, all the layers are uncolored. Takahashi is going to paint some of the layers in red, green or blue to make a beautiful tower.
He defines the beauty of the tower as follows:

The beauty of the tower is the sum of the scores of the N layers, where the score of a layer is A if the layer is painted red, A+B if the layer is painted green, B if the layer is painted blue, and 0 if the layer is uncolored.

Here, A and B are positive integer constants given beforehand. Also note that a layer may not be painted in two or more colors.

Takahashi is planning to paint the tower so that the beauty of the tower becomes exactly K.
How many such ways are there to paint the tower? Find the count modulo 998244353.
Two ways to paint the tower are considered different when there exists a layer that is painted in different colors, or a layer that is painted in some color in one of the ways and not in the other.

Constraints

1 ≤ N ≤ 3×10^5

1 ≤ A,B ≤ 3×10^5

0 ≤ K ≤ 18×10^{10}

All values in the input are integers.

Input

Input is given from Standard Input in the following format:

N A B K

Output

Print the number of the ways to paint tiles, modulo 998244353.

Sample Input 1

4 1 2 5

Sample Output 1

40

In this case, a red layer worth 1 points, a green layer worth 3 points and the blue layer worth 2 points. The beauty of the tower is 5 when we have one of the following sets of painted layers:

1 green, 1 blue

1 red, 2 blues

2 reds, 1 green

3 reds, 1 blue

The total number of the ways to produce them is 40.

Sample Input 2

2 5 6 0

Sample Output 2

1

The beauty of the tower is 0 only when all the layers are uncolored. Thus, the answer is 1.

Sample Input 3

90081 33447 90629 6391049189

Sample Output 3

577742975

Solution in C# (Mono 4.6.2.0) (judge verdict: Time Limit Exceeded)

using System;
using System.IO;
using System.Collections.Generic;

namespace AGC025B_1
{
    public class Program
    {
        void Solve(StreamScanner ss, StreamWriter sw)
        {
            //---------------------------------
            //12976 252925 5381 739707146
            //243286 169958 277609 953521533
            var N = ss.Next(int.Parse);
            var A = ss.Next(long.Parse);
            var B = ss.Next(long.Parse);
            var K = ss.Next(long.Parse);

            ModInt.Mod = 998244353;
            var comb = new Combination(N * 2);

            var ans = (ModInt)0;
            for (var a = 0; a <= N; a++)
            {
                if ((K - a * A) % B != 0) continue;
                var b = (K - a * A) / B;
                if (0 > b || b > N) continue;
                ans += comb.NCK(N, a) * comb.NCK(N, (int)b);
            }

            sw.WriteLine(ans);
            //---------------------------------
        }

        static void Main()
        {
            var ss = new StreamScanner(new StreamReader(Console.OpenStandardInput()));
            var sw = new StreamWriter(Console.OpenStandardOutput()) {AutoFlush = false};
            new Program().Solve(ss, sw);
            sw.Flush();
        }

        static readonly Func<string, string> String = s => s;
    }

    public class Combination
    {
        readonly ModInt[] facts;

        public Combination(int max)
        {
            facts = new ModInt[max + 1];
            facts[0] = 1;
            for (var i = 1; i <= max; i++) facts[i] = facts[i - 1] * i;
        }

        public ModInt Fact(int n)
        {
            return facts[n];
        }

        public ModInt NCK(int n, int k)
        {
            if (n < k) return 0;
            return facts[n] / facts[k] / facts[n - k];
        }

        public ModInt NPK(int n, int k)
        {
            if (n < k) return 0;
            return facts[n] / facts[n - k];
        }

        public ModInt NHK(int n, int k)
        {
            if (k == 0) return 1;
            if (n == 0) return 0;
            return facts[n + k - 1] / facts[k] / facts[n - 1];
        }
    }

    public struct ModInt
    {
        public static int Mod = 1000000007;

        readonly long value;
        public int Value { get { return (int)value; } }
        public ModInt Inverse { get { return GetInverse(); } }

        public ModInt(long value)
        {
            value %= Mod;
            this.value = value < 0 ? value + Mod : value;
        }

        ModInt GetInverse()
        {
            if (value == 0) throw new InvalidOperationException("value must NOT equal 0");
            return Pow(Mod - 2);
        }

        public ModInt Square()
        {
            return this * this;
        }

        public ModInt Pow(long exp)
        {
            if (exp == 0) return 1;
            if (exp % 2 == 0) return Pow(exp / 2).Square();
            return this * Pow(exp - 1);
        }

        public static ModInt Parse(string str)
        {
            return long.Parse(str);
        }

        public static implicit operator ModInt(long value)
        {
            return new ModInt(value);
        }

        public static ModInt operator +(ModInt left, ModInt right)
        {
            return left.value + right.value;
        }

        public static ModInt operator -(ModInt left, ModInt right)
        {
            return left.value - right.value;
        }

        public static ModInt operator *(ModInt left, ModInt right)
        {
            return left.value * right.value;
        }

        public static ModInt operator /(ModInt left, ModInt right)
        {
            return left * right.Inverse;
        }

        public override bool Equals(object obj)
        {
            if (!(obj is ModInt)) return false;
            return value == ((ModInt)obj).value;
        }

        public override int GetHashCode()
        {
            return value.GetHashCode();
        }

        public override string ToString()
        {
            return value.ToString();
        }
    }

    public class StreamScanner
    {
        static readonly char[] Sep = {' '};
        readonly Queue<string> buffer = new Queue<string>();
        readonly TextReader textReader;

        public StreamScanner(TextReader textReader)
        {
            this.textReader = textReader;
        }

        public T Next<T>(Func<string, T> parser)
        {
            if (buffer.Count != 0) return parser(buffer.Dequeue());
            var nextStrings = textReader.ReadLine().Split(Sep, StringSplitOptions.RemoveEmptyEntries);
            foreach (var nextString in nextStrings) buffer.Enqueue(nextString);
            return Next(parser);
        }

        public T[] Next<T>(Func<string, T> parser, int x)
        {
            var ret = new T[x];
            for (var i = 0; i < x; ++i) ret[i] = Next(parser);
            return ret;
        }

        public T[][] Next<T>(Func<string, T> parser, int x, int y)
        {
            var ret = new T[y][];
            for (var i = 0; i < y; ++i) ret[i] = Next(parser, x);
            return ret;
        }
    }
}