using namespace std;
#include<bits/stdc++.h>
void _main();int main(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);_main();return 0;}
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
typedef long long ll;typedef long double ld;template<class ll>inline bool chmax(ll&a,ll b){if(a<b){a=b;return 1;}return 0;}template<class ll>inline bool chmin(ll& a,ll b){if(a>b){a=b;return 1;}return 0;}
#define rep1(a)          for(int i = 0; i < a; i++)
#define rep2(i, a)       for(int i = 0; i < a; i++)
#define rep3(i, a, b)    for(int i = a; i < b; i++)
#define rep4(i, a, b, c) for(int i = a; i < b; i += c)
#define overload4(a, b, c, d, e, ...) e
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define ALL(x) std::begin(x),std::end(x)
#define INF ((1LL<<62)-(1LL<<31))
#define bit(x,i) (((x)>>(i))&1)
#define fi first
#define se second
#define pb push_back
#define Endl endl
#define spa " "
#define YesNo(x) cout<<(x?"Yes":"No")<<endl;
inline void scan(){}
template<class Head,class... Tail>
inline void scan(Head&head,Tail&... tail){std::cin>>head;scan(tail...);}
#define LL(...) ll __VA_ARGS__;scan(__VA_ARGS__)
#define STR(...) string __VA_ARGS__;scan(__VA_ARGS__)
template<typename T>
std::istream &operator>>(std::istream&is,std::vector<T>&v){for(T &in:v){is>>in;}return is;}
template<typename T>
std::ostream &operator<<(std::ostream&os,const std::vector<T>&v){for(auto it=std::begin(v);it!=std::end(v);){os<<*it<<((++it)!=std::end(v)?" ":"");}return os;}
long double my_distance(long double xi,long double yi,long double xj,long double yj){return sqrt(abs((xi-xj)*(xi-xj))+abs((yi-yj)*(yi-yj)));}
void print(){
    cout << '\n';
}
template<class T, class... Ts>
void print(const T& a, const Ts&... b){
    cout << a;
    (cout << ... << (cout << ' ', b));
    cout << '\n';
}
template<class... T>
constexpr auto min(T... a){
    return min(initializer_list<common_type_t<T...>>{a...});
}
template<class... T>
constexpr auto max(T... a){
    return max(initializer_list<common_type_t<T...>>{a...});
}
//Union-Find from https://zenn.dev/reputeless/books/standard-cpp-for-competitive-programming/vi((b%2==0?b-1:b)+2-(a%2==0?a+1:a))/2er/union-find
class UnionFind{public:UnionFind()=default;explicit UnionFind(size_t n):m_parentsOrSize(n, -1){}int find(int i){if(m_parentsOrSize[i]<0){return i;}return(m_parentsOrSize[i]=find(m_parentsOrSize[i]));}void merge(int a,int b){a=find(a);b=find(b);if(a!=b){if(-m_parentsOrSize[a]<-m_parentsOrSize[b]){std::swap(a,b);}m_parentsOrSize[a]+=m_parentsOrSize[b];m_parentsOrSize[b]=a;}}bool connected(int a,int b){return (find(a)==find(b));}int size(int i){return -m_parentsOrSize[find(i)];}private:std::vector<int>m_parentsOrSize;};
//ll MOD = INF;
//ll MOD = 1000000007;
ll MOD = 998244353;

bool iskaibun(string s){ll k = s.size();rep(i,0,k/2){if(s[i]!=s[k-1-i]){return false;}}return true;}
#include <atcoder/all>
using namespace atcoder;
string replace(const string&moto,const string &from, const string&too) {
  int from_len = from.size();
  string tmp = from + moto;
  int tmp_len = tmp.size();
  vector<int> za = z_algorithm(tmp);
  string ret = "";
  for (int i = from_len; i < tmp_len;) {
    if (za[i] >= from_len) {
      ret += too;
      i += from_len;
    } else {
      ret += tmp[i];
      i++;
    }
  }
  return ret;
}

ll zaatu(vector<ll>&A){
    map<ll,ll>m;
    for(auto&&x:A)m[x]=0;
    ll ret = 0;
    for(auto&&[key,val]:m)val=ret++;
    for(auto&&x:A)x=m[x];
    return ret;
}
//約数列挙
vector<ll>enumdiv(ll n){
    vector<ll>s;
    for(ll i = 1;i*i<=n;i++){
        if(n%i==0){s.push_back(i);if(i*i!=n)s.push_back(n/i);}
        
    }
    return s;
}
vector<ll> topo_sort(vector<vector<ll>>&G,vector<ll>&nyu_cnt,ll v){
    vector<ll>ret;
    priority_queue<ll,vector<ll>,greater<ll>>pq;
    rep(i,0,v){
        if(nyu_cnt[i]==0)pq.push(i);
    }
    while(!pq.empty()){
        ll pos = pq.top();pq.pop();
        for(ll i:G[pos]){
            nyu_cnt[i]--;
            if(nyu_cnt[i]==0)pq.push(i);
        }
        ret.push_back(pos);
    }
    return ret;
}
vector<pair<ll,ll>> soinsu_bunkai(ll x){
    vector<pair<ll,ll>>ret;
    rep(i,2,sqrt(x)+1){
        if(x%i==0){
            ll cnt{};
            while(x%i==0){
                x/=i;
                cnt++;
            }
            ret.push_back({i,cnt});
        }
    }
    if(x!=1)ret.push_back({x,1});
    return ret;
}

const int MAX = 510000;

long long fac[MAX], finv[MAX], inv[MAX];
void COMinit(){
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
vector<bool> isprime;
vector<int> Era(int n) {
    isprime.resize(n, true);
    vector<int> res;
    isprime[0] = false; isprime[1] = false;
    for (int i = 2; i < n; ++i) isprime[i] = true;
    for (int i = 2; i < n; ++i) {
        if (isprime[i]) {
            res.push_back(i);
            for (int j = i*2; j < n; j += i) isprime[j] = false;
        }
    }
    return res;
}
using mint = modint998244353;

void _main(){
    LL(x,y,z,w);
    mint ans = 1;
    for(int i = x;i>z;i--)ans*=i;
    for(int i = y;i>w;i--)ans*=i;
    COMinit();
    if(z==0) ans *= COM(x+y-z-w-1,x-1);
    else ans *= COM(x+y-z-w-1,y-1);
    cout<<ans.val()<<endl;
}