#include <bits/stdc++.h>
typedef long long ll;
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,a) FOR(i,0,a)

using namespace std;
const ll MOD=1e9+7;
const int MAX_N=3e5,MAX_M=1e6;
ll fact[MAX_N+MAX_M],ifact[MAX_N+MAX_M];
int N,M,D1,D2,D;
ll minv(ll n){
	ll m=MOD-2,ret=1;
	while(m){
		if(m&1){
			ret*=n;
			ret%=MOD;
		}
		n*=n;
		n%=MOD;
		m>>=1;
	}
	return ret;
}
ll cmb(ll n,ll m){
	return fact[n]*ifact[m]%MOD*ifact[n-m]%MOD;
}
int main(){
	cin>>N>>M>>D1>>D2;
	D=D2-D1;
	ll x=M-1-(ll)D1*(N-1);
	ll ans=0;
	fact[0]=1;
	REP(i,N+M-1){
		fact[i+1]=fact[i]*(i+1)%MOD;
	}
	ifact[N+M-1]=minv(fact[N+M-1]);
	for(int i=N+M-2;i>=0;i--){
		ifact[i]=ifact[i+1]*(i+1)%MOD;
	}
	REP(i,N){
		ll sgn;
		if(i%2==0){
			sgn=1;
		}else{
			sgn=-1;
		}
		ll y=x-(ll)i*(D+1)+N;
		if(y-N>=0){
			ans+=sgn*(cmb(N-1,i)*cmb(y,N))%MOD;
			ans+=MOD;
			ans%=MOD;
		}
	}
	cout<<ans<<endl;
}