#include #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 using _pq = priority_queue, greater>; template ll LB(vector &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();} template ll UB(vector &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();} template bool chmin(T &a,T b){if(a>b){a=b;return 1;}else return 0;} template bool chmax(T &a,T b){if(a void So(vector &v) {sort(v.begin(),v.end());} template void Sore(vector &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 void vec_out(vector &p,int ty=0){ if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'< T vec_min(vector &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;} template T vec_max(vector &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;} template T vec_sum(vector &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"; }