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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

// using System.Numerics;
using System.Runtime.CompilerServices;
using System.Diagnostics;
using ll=System.Int64;
using static Contest_B.Lib_IO;
using static Contest_B.Lib_Minifunc;



public static class Contest_B
{

	public static void Main() {
		checked{
			long n, a,b,k;
			Lib_IO.rm(out n, out a,out b,out k);

			ModCombination mc = new ModCombination(n+2,MOD1);

			long ans = 0;
			for (ll rn = 0; rn <= n; rn++)
			{
				ll bn = k - a*rn;
				if(bn%b==0){
					bn = bn /= b;
					ans = (ans+ (mc.C(n,rn)*mc.C(n,bn).Value)%MOD1);
				}
				
			}





			Lib_IO.wm(ans%MOD1);
		}
	}




public struct ModInt {
	public readonly long Value, Modulo;
//	public System.Numerics.BigInteger Value, Modulo;

	public ModInt(long value) : this(value, long.MaxValue) {}
	public ModInt(long value, long modulo) {
//	public ModInt(System.Numerics.BigInteger value, System.Numerics.BigInteger modulo) {
		if (modulo<2) throw new ArgumentException("Invalid modulo", "modulo");
		this.Value = value % modulo;
		if(this.Value < 0) this.Value += modulo;
		this.Modulo = modulo;
	}

	public static implicit operator long(ModInt a) => a.Value;
	public static ModInt operator-(ModInt a) => new ModInt(-1*a.Value, a.Modulo); 
	public static ModInt operator+(ModInt a, ModInt b) => new ModInt(a.Value + b.Value, a.Modulo==b.Modulo?a.Modulo:-1); 
	public static ModInt operator-(ModInt a, ModInt b) => new ModInt(a.Value - b.Value, a.Modulo==b.Modulo?a.Modulo:-1); 
	public static ModInt operator*(ModInt a, ModInt b) => new ModInt(a.Value * b.Value, a.Modulo==b.Modulo?a.Modulo:-1); 
	public static ModInt operator/(ModInt a, ModInt b) => a * b.Inverse();
	public static ModInt operator+(ModInt a, long c) => new ModInt(a.Value + c, a.Modulo); 
	public static ModInt operator-(ModInt a, long c) => new ModInt(a.Value - c, a.Modulo); 
	public static ModInt operator*(ModInt a, long c) => new ModInt(a.Value * c, a.Modulo); 
	public static ModInt operator/(ModInt a, long c) => a * (new ModInt(c, a.Modulo)).Inverse(); 
	public static bool operator==(ModInt a, ModInt b) => a.Equals(b);
	public static bool operator!=(ModInt a, ModInt b) => !a.Equals(b);

	public ModInt Inverse() {
		long a = this.Value, b = this.Modulo, u = 1, v = 0, t, s;
//		System.Numerics.BigInteger a = this.Value, b = this.Modulo, u = 1, v = 0, t, s;
		while(b > 0) {
			t = a / b;
			s = a - t * b; a = b; b = s;
			s = u - t * v; u = v; v = s;
		}
		return new ModInt(u, this.Modulo);
	}

	public ModInt Pow(long n) {
		ModInt ret = new ModInt(1, this.Modulo);
		ModInt mul = this;
		while(n > 0) {
			if((n & 1)==1) ret *= mul;
			mul *= mul;
			n >>= 1;
		}
		return ret;
	}

	public override bool Equals(object obj) {
		if (!(obj is ModInt)) throw new ArgumentException("Object is not ModInt type");
		return Equals((ModInt)obj);   
	}
	public bool Equals(ModInt p) {
		if (this.Modulo != p.Modulo) throw new ArgumentException("Modulo is not Equal");
		return (this.Value == p.Value);
	}
	public override int GetHashCode() => (int)(this.Value ^ this.Modulo);
	public override string ToString() => this.Value.ToString();

}


// n! nPr nCr nHr B(n,k) S{nk} P(n,k) を求める。
// ModCombinationは結果をmod	 ※ ModInt クラスが必要
// ベル数 B(n,k)
//   区別できる n個のボールを区別できない k個以下の箱に分割する方法の数を与える。
//   特に B(n,n)は n 個のボールを任意個のグループに分割する方法の数である。
// 第2種スターリング数 S{nk}
//   区別できる n 個のボールを区別できない k 個の箱に分割する方法の数を与える。
// 分割数テーブル
//   分割数 P(n,k) は整数 n をちょうど k 個の非負整数の和で表す方法の数を与える。
//   順序が異なるものは同一視する。
// 攪乱順列（モンモール数）
//   数字の並びを完全にかくらんする（もとと同じ場所になる要素がない）順列
public class ModCombination {
	private ModInt[] _fact, _rfact, _inv, _seq;

	public ModCombination(long sz) : this(sz, long.MaxValue) {}
	public ModCombination(long sz, long modulo){
		_fact = new ModInt[sz+1];
		_rfact = new ModInt[sz+1];
		_inv = new ModInt[sz+1];
		_seq = new ModInt[sz+1];

		for(int i = 0; i <= sz; i++) _seq[i] = new ModInt(i,modulo);
		_fact[0] = _rfact[sz] = _inv[0] = _seq[1];
		for(int i = 1; i <= sz; i++) _fact[i] = _fact[i - 1] * i;
		_rfact[sz] /= _fact[sz];
		for(int i = (int)sz - 1; i >= 0; i--) _rfact[i] = _rfact[i + 1] * (i + 1);
		for(int i = 1; i <= sz; i++) _inv[i] = _rfact[i] * _fact[i - 1];
	}

	public ModInt Fact(long n) {
		if(n < 2) return _seq[1];
		return _fact[n];
	}
	public ModInt P(long n, long k) {
		if(k < 0 || n < k) return _seq[0];
		return _fact[n] * _rfact[n - k];
	}
	public ModInt C(long n, long k) {
		if(k < 0 || n < k) return _seq[0];
		return _fact[n] * _rfact[k] * _rfact[n - k];
	}
	public ModInt H(long n, long k) {
		if(n < 0 || k < 0) return _seq[0];
		return k == 0 ? _seq[1] : C(n + k - 1, k);
	}
	public ModInt B(long n, long k) {
		if(n == 0) return _seq[1];
		k = k<n ? k : n;
		ModInt ret = _seq[0];
		ModInt[] pref = new ModInt[k + 1];
		pref[0] = _seq[1];
		for(int i = 1; i <= k; i++) {
			if((i & 1)==1) pref[i] = pref[i - 1] - _rfact[i];
			else pref[i] = pref[i - 1] + _rfact[i];
		}
		for(int i = 1; i <= k; i++) ret += _seq[i].Pow(n) * _rfact[i] * pref[k - i];
		return ret;
	}
	public ModInt S(long n, long k) {
		if (n < 0 || k < 0 || n < k) return _seq[0];
		ModInt ret = _seq[0];
		for(int i = 0; i <= k; i++) {
			ModInt add = _seq[i].Pow(n) * this.C(k, i);
			if(((k - i) & 1)==1) ret -= add;
			else ret += add;
		}
		return ret * _rfact[k];
	}
	public static ModInt[][] PartitionTable(long n, long k, long modulo=long.MaxValue) {
		ModInt[][] dp = new ModInt[n + 1][];
		for(int i=0;i<=n;i++) dp[i] = Enumerable.Repeat(new ModInt(0,modulo), (int)k+1).ToArray();
		dp[0][0] = new ModInt(1, modulo);
		for(int i = 0; i <= n; i++) {
			for(int j = 1; j <= k; j++) {
				if(i - j >= 0) dp[i][j] = dp[i][j - 1] + dp[i - j][j];
				else dp[i][j] = dp[i][j - 1];
			}
		}
		return dp;
	}
	public static long MontmortNumber(long n, long modulo=long.MaxValue) {
		if(n<=3) return Math.Max(0,n-1);
		else{
			long a1 = 1, a2 = 2, a3 = 0;
			for (long i = 4; i <= n; i++) {
				a3 = ((i-1)*(a2+a1))%modulo;
				a1 = a2;
				a2 = a3; 
			}
			return a3;
		}
	}


}















#region BaseModule


public static class Lib_Minifunc{
	[MethodImpl(256)] public static void swap1<T>(ref T a, ref T b) { T t = a; a = b; b = t; }
	[MethodImpl(256)] public static void swap2<T>(ref T a, ref T b) where T : IComparable { if (a.CompareTo(b)==1) swap1(ref a, ref b); }  // b の方が小さければ交換
	[MethodImpl(256)] public static bool chmin<T>(ref T a, T b) where T : IComparable { if (a.CompareTo(b)== 1) { a = b; return true; } return false; }  // b の方が小さければ a を更新
	[MethodImpl(256)] public static bool chmax<T>(ref T a, T b) where T : IComparable { if (a.CompareTo(b)==-1) { a = b; return true; } return false; }  // b の方が大きければ a を更新
	[MethodImpl(256)] public static bool inside(long i, long n) => (0<=i&&i<n);
	[MethodImpl(256)] public static bool inside(long x, long y, long w, long h) => (inside(x,w)&&inside(y,h));
	[MethodImpl(256)] public static T min<T>(params T[] a) where T : IComparable => a.Min();
	[MethodImpl(256)] public static T max<T>(params T[] a) where T : IComparable => a.Max();
	[MethodImpl(256)] public static long mod(long a, long m=MOD1) { var v = a%m; return (v<0?v+m:v); }
	[MethodImpl(256)] public static long ceiling(long a, long b) => (a%b==0?a/b:a/b+1);	// 整数商の切り上げ
	[MethodImpl(256)] public static P<T,U> initp<T,U>(T a,U b) => new P<T,U>(a,b);
	[MethodImpl(256)] public static P<T,U,V> initp<T,U,V>(T a,U b,V c) => new P<T,U,V>(a,b,c);
	[MethodImpl(256)] public static P<T,U,V,W> initp<T,U,V,W>(T a,U b,V c,W d) => new P<T,U,V,W>(a,b,c,d);
	[MethodImpl(256)] public static bool initd<T,U>(Dictionary<T,U> d, T k) { if(d.ContainsKey(k)) { return false; } else { d[k] = default(U); return true; } }
	public static T[] inita<T>(long len1) where T : new() { var m = new T[len1]; for (int i=0;i<m.Length;i++) m[i] = new T(); return m; }
	public static T[][] initm<T>(long len1,long len2,T val) where T : struct { var m = new T[len1][]; for (int i=0;i<m.Length;i++) m[i] = Enumerable.Repeat(val,(int)len2).ToArray(); return m; }
	public static T[][][] initm<T>(long len1,long len2,long len3,T val) where T : struct { var m = new T[len1][][]; for (int i=0;i<m.Length;i++) m[i] = initm(len2,len3,val); return m; }
	public const long MOD1 = 998244353; 
	public const double EPS1 = 1e-8;
	public const long INF1 = 1000000000000000;  // 10^15
}

public struct P<T,U>
{
	public T A; public U B;
	public P(T a,U b) { A = a; B = b; }
	public static implicit operator KeyValuePair<T,U>(P<T,U> a) => new KeyValuePair<T,U>(a.A,a.B);
	public static implicit operator P<T,U>(KeyValuePair<T,U> a) => new P<T,U>(a.Key,a.Value);
}
public struct P<T,U,V>
{
	public T A; public U B; public V C;
	public P(T a,U b,V c) { A = a; B = b; C = c; }
}
public struct P<T,U,V,W>
{
	public T A; public U B; public V C; public W D;
	public P(T a,U b,V c,W d) { A = a; B = b; C = c; D = d; }
}

public static class Lib_IO
{
	class Prt : System.IO.StreamWriter
	{
		public override IFormatProvider FormatProvider { get { return System.Globalization.CultureInfo.InvariantCulture; } }
		public Prt(System.IO.Stream s) : base(s,new UTF8Encoding(false,true)) {}
		public Prt(System.IO.Stream s,Encoding e) : base(s,e) {}
	}
	static Prt sw = new Prt(Console.OpenStandardOutput());
	static char[] sp = new char[] {' '};
	[MethodImpl(256)] static bool eq<T,U>() => typeof(T).Equals(typeof(U));
	[MethodImpl(256)] static T ct<T,U>(U a) => (T)Convert.ChangeType(a,typeof(T));
	[MethodImpl(256)] static T cv<T>(string s) =>
		eq<T,int>()	? ct<T,int>(int.Parse(s))
	  : eq<T,long>()   ? ct<T,long>(long.Parse(s))
	  : eq<T,double>() ? ct<T,double>(double.Parse(s,System.Globalization.CultureInfo.InvariantCulture))
	  : eq<T,char>()   ? ct<T,char>(s[0])
					   : ct<T,string>(s);
	public static string[] rm<T>(out T a) {
		var z = Console.ReadLine().Split(sp,StringSplitOptions.RemoveEmptyEntries); 
		a = cv<T>(z[0]);
		return z;
	}
	public static string[] rm<T,U>(out T a,out U b) {
		var z = rm<T>(out a); 
		b = cv<U>(z[1]);
		return z;
	}
	public static string[] rm<T,U,V>(out T a,out U b,out V c) {
		var z = rm<T,U>(out a,out b); 
		c = cv<V>(z[2]);
		return z;
	}
	public static string[] rm<T,U,V,W>(out T a,out U b,out V c,out W d) {
		var z = rm<T,U,V>(out a,out b,out c); 
		d = cv<W>(z[3]);
		return z;
	}
	public static string[] rm<T,U,V,W,X>(out T a,out U b,out V c,out W d,out X e) {
		var z = rm<T,U,V,W>(out a,out b,out c,out d); 
		e = cv<X>(z[4]);
		return z;
	}
	public static string[] rm<T,U,V,W,X,Y>(out T a,out U b,out V c,out W d,out X e,out Y f) {
		var z = rm<T,U,V,W,X>(out a,out b,out c,out d,out e); 
		f = cv<Y>(z[5]);
		return z;
	}
	public static string[] ra<T>(out T[] a) {		
		var z = Console.ReadLine().Split(sp,StringSplitOptions.RemoveEmptyEntries);
		a = z.Select(cv<T>).ToArray();
		return z;
	}
	public static string[][] rl<T>(long n,out T[] a) {
		a = new T[n];
		var y = new string[n][];
		for(int i=0;i<n;i++) y[i] = rm(out a[i]);
		return y;
	}
	public static string[][] rl<T,U>(long n,out P<T,U>[] a) {
		a = new P<T,U>[n];
		var y = new string[n][];
		for(int i=0;i<n;i++) {
			T o; U p;
			y[i] = rm(out o,out p);
			a[i] = new P<T,U>(o,p);
		}
		return y;
	}
	public static string[][] rl<T,U,V>(long n,out P<T,U,V>[] a) {
		a = new P<T,U,V>[n];
		var y = new string[n][];
		for(int i=0;i<n;i++) {
			T o; U p; V q;
			y[i] = rm(out o,out p,out q);
			a[i] = new P<T,U,V>(o,p,q);
		}
		return y;
	}
	public static string[][] rl<T,U,V,W>(long n,out P<T,U,V,W>[] a) {
		a = new P<T,U,V,W>[n];
		var y = new string[n][];
		for(int i=0;i<n;i++) {
			T o; U p; V q; W r;
			y[i] = rm(out o,out p,out q,out r);
			a[i] = new P<T,U,V,W>(o,p,q,r);
		}
		return y;
	}
	public static string[][] rx<T>(long n,out T[][] a) {
		a = new T[n][];
		var y = new string[n][];
		for(int i=0;i<n;i++) y[i] = ra(out a[i]);
		return y;
	}

	static void wwp(Action act){
		sw.AutoFlush = false;
		Console.SetOut(sw);
		act();
		Console.Out.Flush();
		sw.AutoFlush = true;
		Console.SetOut(sw);
	}
	[MethodImpl(256)] static string wfm(Type t) =>t.Equals(typeof(double)) ? "{0:F10}" : "{0}";
	public static void wm(params object[] a) {
		wwp(()=>{
			for(int i=0;i<a.Length-1;i++) Console.Write(wfm(a[i].GetType())+" ",a[i]);
			Console.WriteLine(wfm(a[a.Length-1].GetType()),a[a.Length-1]);
		});
	}
	public static void wa<T>(IList<T> a) { wxa(new IList<T>[]{a}, " "); }
	public static void wl<T>(IList<T> a) {
		wwp(()=>{
			var f = wfm(typeof(T));
			foreach(T x in a) Console.WriteLine(f,x);
		});
	}
	static void wxa<T>(IList<IList<T>> a, string s) {
		wwp(()=>{
			var f = wfm(typeof(T));
			var g = f + s;
			foreach(var b in a) {
				for(int i=0;i<b.Count-1;i++) Console.Write(g,b[i]);
				Console.WriteLine(f,b[b.Count-1]);
			}
		});
	}
	public static void wx<T>(IList<IList<T>> a) { wxa(a, " "); }
	public static void wg<T>(IList<IList<T>> a) { wxa(a, ""); }
}

#endregion



}