#define MD 998244353
Mint f(ll h,ll a){
	Mint r;
	rep(i,h){
		r+=(Mint(min(h-a+1,i+1)-max(0,i-a+1))/(h-a+1))**2;
	}
	return r;
}
{
	ll@h,@w,@a,@b;
	wt(2a*b-f(h,a)*f(w,b));
}