#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using db = long double;
using ch = char;
using bl = bool;
using st = string;
using pll = pair<ll,ll>;
using psl = pair<st,ll>;
using vst = vector<st>;
using vch = vector<ch>;
using vvch = vector<vch>;
using vbl = vector<bl>;
using vvbl = vector<vbl>;
using vdb = vector<db>;
using vpll = vector<pll>;
using vvpll = vector<vpll>;
using vpsl = vector<psl>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vvvvll = vector<vvvll>;
using vvvvvll = vector<vvvvll>;
#define all(A) A.begin(),A.end()
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define rrep(i,a,b) for(ll i=(ll)(a);i<=(ll)(b);i++)
#define drep(i,n) for(ll i=(ll)n-1; i>=0; i--)
#define drrep(i,a,b) for(ll i=(ll)a; i>=(ll)b; i--)

using mint = modint998244353;
// using mint = modint1000000007;
using vm = vector<mint>;
using vvm = vector<vm>; 
using vvvm = vector<vvm>;

const ll mod = 998244353;
const ll INF = 3e18;

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;
}

ll gcd(ll a, ll b) {
	if (a==0)return b;
	if (b==0)return a;
	ll c=a;
	while(a%b!=0){
		c=a%b;
		a=b;
		b=c;
	}
	return b;
}

ll lcm(ll a,ll b){
	return a/gcd(a,b)*b;
}

ll Pow(ll a, ll n){
	ll res=1;
	while(n>0){
		if(n%2==1)res*=a;
		a*=a;
		n/=2;
	}
	return res;
}

ll Pow(ll a, ll n, ll p){
	ll res=1;
	while(n>0){
		a%=p;
		if(n%2==1)res*=a;
		a*=a;
		res%=p;
		n/=2;
	}
	return res;
}

void yn(bl ok){
	if(ok==true){
		cout << "Yes" << endl;
	}
	else{
		cout << "No" << endl;
	}
	return;
}

vector<mint> fact,factinv,inv;
void combination(ll n){
	fact.resize(n+5);
	factinv.resize(n+5);
	inv.resize(n+5);
	fact[0]=fact[1]=1;
	factinv[0]=factinv[1]=1;
	inv[1]=1;
	rrep(i,2,n+4){
		fact[i]=fact[i-1]*i;
		inv[i]=mod-(inv[mod%i]*(mod/i));
		factinv[i]=factinv[i-1]*inv[i];
	}
}

mint nCr(ll n, ll r){
	mint res=fact[n];
	res*=factinv[r]*factinv[n-r];
	return res;
}


ll X,Y,Z,W;

int main(){
	cin>>X>>Y>>Z>>W;
	combination(X+Y);
	mint ans=1;
	if(Z==0)
	{
		ans*=X;
		ans*=nCr(Y,W)*fact[X+Y-Z-W-1];
	}
	else
	{
		ans*=Y;
		ans*=nCr(X,Z)*fact[X+Y-Z-W-1];
	}
	cout << ans.val() << endl;
	return 0;
}