#include<iostream>
using namespace std;
long mod=1e9+7;
long N,M,D1,D;
const int LIM=1301000;
long F[LIM],I[LIM];
long power(long a,long b){return b?power(a*a%mod,b/2)*(b%2?a:1)%mod:1;}
long comb(long N,long K){return N<K||N<0||K<0?0L:F[N]*I[K]%mod*I[N-K]%mod;}
long H(long N,long K)
{
	return K==0?1L:comb(N+K-1,K);
}
main()
{
	F[0]=1;
	for(int i=1;i<LIM;i++)F[i]=F[i-1]*i%mod;
	I[LIM-1]=power(F[LIM-1],mod-2);
	for(int i=LIM-1;i--;)I[i]=I[i+1]*-~i%mod;
	cin>>N>>M>>D1>>D;
	M--;
	D-=D1;
	M-=(N-1)*D1;
	long ans=0;
	for(int i=0;i<N;i++)
	{
		long now=comb(N-1,i)*H(N+1,M-(long)i*(D+1))%mod;
		if(i%2==0)ans+=now;
		else ans-=now;
	}
	cout<<(ans%mod+mod)%mod<<endl;
}