#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;
 
#include<bits/stdc++.h>
using namespace std;

const int MOD=998244353;
ll modpow(ll x,ll n){
  x%=MOD;
  ll ans=1;
  while(n){
    if(n&1) ans=ans*x%MOD;
    x=x*x%MOD;
    n/=2;
  }
  return ans;
}

int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  
  ll h,w,a,b;
  cin>>h>>w>>a>>b;
  ll h1=0,h2=0,w1=0,w2=0;
  ll x=(h-a+1)*(w-b+1)%MOD;
  ll mh=min(a,h-a+1),mw=min(b,w-b+1);
  rep(i,h){
    ll th=min(mh,min((ll)i+1,h-i));
    h1=(h1+th)%MOD;
    th=th*th%MOD;
    h2=(h2+th)%MOD;
  }
  rep(j,w){
    ll tw=min(mw,min((ll)j+1,w-j));
    w1=(w1+tw)%MOD;
    tw=tw*tw%MOD;
    w2=(w2+tw)%MOD;
  }
  ll ans=2*modpow(x,MOD-2)%MOD*h1%MOD*w1%MOD;
  ans=(ans+MOD-modpow(x*x,MOD-2)*h2%MOD*w2%MOD)%MOD;
  cout<<ans<<endl;
    
  return 0;
}