#include <bits/stdc++.h>
//#include<boost/multiprecision/cpp_int.hpp>
//#include<boost/multiprecision/cpp_dec_float.hpp>
//#include <atcoder/all>
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i)
#define repl(i, a) for (ll i = (ll)0; i < (ll)a; ++i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define popcount __builtin_popcount
#define fi first
#define se second
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll mod_998244353 = 998244353;
constexpr ll INF = 1LL << 60;

// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")

//using lll=boost::multiprecision::cpp_int;
//using Double=boost::multiprecision::number<boost::multiprecision::cpp_dec_float<1024>>;//仮数部が1024桁
template <class T>
inline bool chmin(T &a, T b)
{
	if (a > b)
	{
		a = b;
		return true;
	}
	return false;
}
template <class T>
inline bool chmax(T &a, T b)
{
	if (a < b)
	{
		a = b;
		return true;
	}
	return false;
}

template <typename T>
T mypow(T x, T n, const T &p = -1)
{ //x^nをmodで割った余り

	if (p != -1)
	{
		x %= p;
	}
	T ret = 1;
	while (n > 0)
	{
		if (n & 1)
		{
			if (p != -1)
				ret = (ret * x) % p;
			else
				ret *= x;
		}
		if (p != -1)
			x = (x * x) % p;
		else
			x *= x;
		n >>= 1;
	}
	return ret;
}

using namespace std;
//using namespace atcoder;

template<int mod>
struct Modint{
    int x;
    Modint():x(0){}
    Modint(int64_t y):x((y%mod+mod)%mod){}

    Modint &operator+=(const Modint &p){
			if((x+=p.x)>=mod)
				x -= mod;
			return *this;
		}

		Modint &operator-=(const Modint &p){
			if((x+=mod-p.x)>=mod)
				x -= mod;
			return *this;
		}

		Modint &operator*=(const Modint &p){
			x = (1LL * x * p.x) % mod;
			return *this;
		}

		Modint &operator/=(const Modint &p){
			*this *= p.inverse();
			return *this;
		}

		Modint operator-() const { return Modint(-x); }
		Modint operator+(const Modint &p) const{
			return Modint(*this) += p;
		}
		Modint operator-(const Modint &p) const{
			return Modint(*this) -= p;
		}
		Modint operator*(const Modint &p) const{
			return Modint(*this) *= p;
		}
		Modint operator/(const Modint &p) const{
			return Modint(*this) /= p;
		}

		bool operator==(const Modint &p) const { return x == p.x; }
		bool operator!=(const Modint &p) const{return x != p.x;}

		Modint inverse() const{//非再帰拡張ユークリッド
			int a = x, b = mod, u = 1, v = 0;
			while(b>0){
				int t = a / b;
				swap(a -= t * b, b);
				swap(u -= t * v, v);
			}
			return Modint(u);
		}

		Modint pow(int64_t n) const{//繰り返し二乗法
			Modint ret(1), mul(x);
			while(n>0){
				if(n&1)
					ret *= mul;
				mul *= mul;
				n >>= 1;
			}
			return ret;
		}

		friend ostream &operator<<(ostream &os,const Modint &p){
			return os << p.x;
		}
};

using modint = Modint<mod>;
using modint2= Modint<mod_998244353>;

template<typename T>
struct Combination{
  //Modint用
  //構築O(N),クエリO(1)
	vector<T>fact,rfact;

	Combination(int64_t n):fact(n+1),rfact(n+1){
		fact[0]=1;fact[1]=1;
		rfact[n]=1;
		for(int64_t i=2;i<=n;++i){
			fact[i]=fact[i-1]*i;
		}
		rfact[n]/=fact[n];
		for(int64_t i=n-1;i>=0;--i){
			rfact[i]=rfact[i+1]*(i+1);
		}
	}

	T C(int64_t n,int64_t r) const{
		if(n==-1&&r==0)return 1;//0H0のとき
		if(r<0 || n<r)return 0;
		return fact[n]*rfact[n-r]*rfact[r];
	}
};


void solve()
{	
	ll n,m,a,b;
	cin>>n>>m>>a>>b;
	modint2 ans=0;
	Combination<modint2>c(m+b+n+5);
	for(ll i=1;i<=m;++i){
		ll x=min(m-i,b)-(n-1)*a;
		modint2 res=1;
		res*=c.C(x+n-1,x);
		res*=c.fact[n];
		ans+=res;
	}
	cout<<ans<<"\n";
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}