#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using vin=vector<int>;
using vll=vector<long long>;
using vvin=vector<vector<int>>;
using vvll=vector<vector<long long>>;
using vstr=vector<string>;
using vvstr=vector<vector<string>>;
using vch=vector<char>;
using vvch=vector<vector<char>>;
using vbo=vector<bool>;
using vvbo=vector<vector<bool>>;
using vpii=vector<pair<int,int>>;
using pqsin=priority_queue<int,vector<int>,greater<int>>;
#define mp make_pair
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rep2(i,s,n) for(int i=(s);i<(int)(n);i++)
#define all(v) v.begin(),v.end()
#define decp(n) cout<<fixed<<setprecision((int)n)
const ll inf=1e9+7;
const ll INF=1e18;
const ll mod=998244353;

const int MAX=510000;

vll fac(MAX);
vll finv(MAX);
vll inv(MAX);

void combinit(ll m){
    fac[0]=1;fac[1]=1;
    finv[0]=1;finv[1]=1;
    inv[1]=1;
    rep2(i,2,MAX){
        fac[i]=fac[i-1]*i%m;
        inv[i]=m-inv[m%i]*(m/i)%m;
        finv[i]=finv[i-1]*inv[i]%m;
    }
}

ll combi(ll n,ll k,ll m=inf){
    if(n<k)return 0;
    if(n<0||k<0)return 0;
    return fac[n]*(finv[k]*finv[n-k]%m)%m;
}

int main(){
    ll n,m,a,b;cin>>n>>m>>a>>b;
    combinit(mod);
    ll ans=(ll)0;
    for(ll i=1;i<=m;i++)ans+=combi(min(i+b,m)+n-2-i-(n-1)*a+1,n-1,mod);
    ans%=mod;
    ans*=fac[n];
    cout<<ans%mod<<endl;
}