#include <iostream>
#include <map>
#include <set>
#include <queue>
#include <cmath>
#include <vector>
#include <string>
#include <algorithm>
#include <functional>
using namespace std;
#pragma warning (disable: 4996)

long long modpow(long long a, long long b, long long m) {
	long long p = 1, q = a;
	for (int i = 0; i < 63; i++) {
		if ((b / (1LL << i)) % 2LL == 1) { p *= q; p %= m; }
		q *= q; q %= m;
	}
	return p;
}

long long Div(long long a, long long b, long long m) {
	return (a * modpow(b, m - 2, m)) % m;
}

long long mod = 998244353;
long long fact[1 << 19];
long long factinv[1 << 19];

// 入力
long long N, M, A, B;
long long Answer = 0;

long long ncr(long long n, long long r) {
	if (r < 0 || n < r) return 0;
	return (fact[n] * factinv[r] % mod) * factinv[n - r] % mod;
}

int main() {
	// Step #1. 入力・調整
	cin >> N >> M >> A >> B;
	M -= (N - 1) * (A - 1);
	B -= (N - 1) * (A - 1);

	// Step #2. 階乗の計算
	fact[0] = 1;
	for (int i = 1; i <= 300000; i++) fact[i] = (1LL * i * fact[i - 1]) % mod;
	for (int i = 0; i <= 300000; i++) factinv[i] = Div(1, fact[i], mod);

	// Step #3. 動的計画法
	for (int i = 1; i <= M; i++) {
		long long kosuu = min(B + 1LL, M - i + 1LL);
		long long ret = ncr(kosuu - 1, N - 1);
		Answer += ret;
		Answer %= mod;
	}

	// Step #4. 出力
	long long FinalAns = Answer * fact[N] % mod;
	cout << FinalAns << endl;
	return 0;
}