#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef int64_t lint;
#define rep(i, n) for(int i=0; i<n; i++)
#define repx(i, l, n) for(int i=l; i<n; i++)
#define all(v) v.begin(), v.end()
#define show(x) cout << #x << ": " << x << endl;
#define list(x) cout << #x << ": " << x << "  ";
#define pb push_back
using vi = vector<lint>;
using vvi = vector<vector<lint>>;
template<class T> inline void vin(vector<T>& v) { rep(i, v.size()) cin >> v.at(i); }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> inline void drop(T x) { cout << x << endl; exit(0); }
template<class T> void vout(vector<T> v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; }
constexpr lint LINF = LLONG_MAX/2;
using mint = modint998244353;
using vm = vector<mint>;

struct combination {
	vector<mint> fact, ifact;
	combination(int n):fact(n+1),ifact(n+1) {
		assert(n < mint::mod());
		fact[0] = 1;
		for (int i = 1; i <= n; ++i) fact[i] = fact[i-1]*i;
		ifact[n] = fact[n].inv();
		for (int i = n; i >= 1; --i) ifact[i-1] = ifact[i]*i;
	}
	mint operator()(int n, int k) {
		if (k < 0 || k > n) return 0;
		return fact[n]*ifact[k]*ifact[n-k];
	}
};

int main() {
	lint X, Y, Z, W;
	cin >> X >> Y >> Z >> W;

	mint a=0, b=0, c=0;
	lint x, y, z;
	combination C(X+Y+1);
	a = C(X, X-Z);
	b = C(Y, Y-W);
	c = 1;
	rep(i, (X+Y)-(Z+W)) c *= i+1;
	if (!Z) std::cout << ((a*b*c)*X/((X+Y)-(Z+W))).val() << '\n';
	if (!W) std::cout << ((a*b*c)*Y/((X+Y)-(Z+W))).val() << '\n';
}