#include <bits/stdc++.h>
#pragma GCC optimize("unroll-loops")
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
const ll ILL=2167167167167167167;
const int INF=2100000000;
const int mod=998244353;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,T b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a,bool upp=0){if(a) cout<<(upp?"YES\n":"Yes\n"); else cout<<(upp?"NO\n":"No\n");}
template<class T> void vec_out(vector<T> &p,int ty=0){
if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";}
else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;}

struct mint{
    static constexpr int  m = 998244353;
    int x;
    mint() : x(0){}
    mint(long long x_):x(x_ % m){if (x < 0) x += m;}
    int val(){return x;}
    mint &operator+=(mint b){if ((x += b.x) >= m) x -= m; return *this;}
    mint &operator-=(mint b){if ((x -= b.x) < 0) x += m; return *this;}
    mint &operator*=(mint b){x= (long long)(x) * b.x % m; return *this;}
    mint pow(long long e) const {
        mint r = 1,b =*this;
        while (e){
            if (e & 1) r *= b;
            b *= b;
            e >>= 1;
        }
        return r;
    }
    mint inv(){return pow(m - 2);}
    mint &operator/=(mint b){return *this *= b.pow(m - 2);}
    friend mint operator+(mint a, mint b){return a += b;}
    friend mint operator-(mint a, mint b){return a -= b;}
    friend mint operator/(mint a, mint b){return a /= b;}
    friend mint operator*(mint a, mint b){return a *= b;}
    friend bool operator==(mint a, mint b){return a.x == b.x;}
    friend bool operator!=(mint a, mint b){return a.x != b.x;}
};


void solve();
// oddloop
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int t=1;
    //cin>>t;
    rep(i,0,t) solve();
}

void solve(){
    ll H,W,A,B;
    cin>>H>>W>>A>>B;
    auto f=[&](ll a,ll b) -> mint {
        mint res=0;
        rep(i,0,a){
            ll L=max(0ll,i-b+1);
            ll R=min(a-b+1,i+1ll);
            res+=(L-R)*(L-R);
        }
        return res/((a-b+1)*(a-b+1));
    };
    cout<<(A*B*2-f(H,A)*f(W,B)).val()<<"\n";
}