#include <bits/stdc++.h>
#include <atcoder/all>
#include <string>

#define rep(i, l, r) for(ll i = (l); i <= (r); i++)
#define rrep(i, l, r) for(ll i = (r); i >= (l); i--)
#define ff first
#define ss second
#define pb push_back
#define ALL(a) (a).begin(),(a).end()

typedef long long ll;

const int INF32 = 2147483647;
const ll INF64 = 9223372036854775807ll;
const int MAX=5100000;

using namespace std;
using namespace atcoder;

const ll MOD=998244353ll;
using mint = modint998244353;



// aよりもbが大きいならばaをbで更新する
// (更新されたならばtrueを返す)
template <typename T>
bool chmax(T &a, const T& b) {
  if (a < b) {
    a = b;  // aをbで更新
    return true;
  }
  return false;
}
// aよりもbが小さいならばaをbで更新する
// (更新されたならばtrueを返す)
template <typename T>
bool chmin(T &a, const T& b) {
  if (a > b) {
    a = b;  // aをbで更新
    return true;
  }
  return false;
}

//cin, cout
void CIN() {};
template <class T, class... U>
void CIN(T &&x, U &&...y) {
  cin >> x;
  CIN(forward<U>(y)...);
}
void _COUT() { cout << '\n'; }
template <class T, class... U>
void _COUT(T &&x, U &&...y) {
  cout << ' ' << x;
  _COUT(forward<U>(y)...);
}
void COUT() { _COUT(); };
template <class T, class... U>
void COUT(T &&x, U &&...y) {
  cout << x;
  _COUT(forward<U>(y)...);
}

vector<long long> fact, fact_inv, inv;
/*  init_nCk :二項係数のための前処理
    計算量:O(n)
*/
void init_nCk(int SIZE) {
    fact.resize(SIZE + 5);
    fact_inv.resize(SIZE + 5);
    inv.resize(SIZE + 5);
    fact[0] = fact[1] = 1;
    fact_inv[0] = fact_inv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < SIZE + 5; i++) {
        fact[i] = fact[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
        fact_inv[i] = fact_inv[i - 1] * inv[i] % MOD;
    }
}
/*  nCk :MODでの二項係数を求める(前処理 int_nCk が必要)
    計算量:O(1)
*/
long long nCk(int n, int k) {
    assert(!(n < k));
    assert(!(n < 0 || k < 0));
    return fact[n] * (fact_inv[k] * fact_inv[n - k] % MOD) % MOD;
}

bool check_grid(ll x, ll y, ll H, ll W){
  if(x < 0 || H <= x){return false;}
  else if(y < 0 || W <= y){return false;}
  return true;
}

int main()
{
	cin.tie(0);	ios::sync_with_stdio(false);
  ll X, Y, Z, W; cin >> X >> Y >> Z >> W;
  init_nCk(1000000);
  mint ans;
  if(Z == 0){ans = nCk(X+Y-Z-W-1, Y-W);}
  else{ans = nCk(X+Y-Z-W-1, X-Z);}

  for(ll i = X; i > Z; i--){ans *= i;}
  for(ll i = Y; i > W; i--){ans *= i;}
  cout << ans.val() << endl;

  return 0;
}