#include <iostream>
using namespace std;

typedef long long ll;

ll inf = 1e9+7;
ll func[2000010] = {0};
ll inv[2000010] = {0};

ll mult(ll n, ll m){
	if(m==1) return n%inf;
	else if(m%2==0){
		ll t = mult(n,m/2);
		return (t*t)%inf;
	}else{
		ll t = mult(n,m-1);
		return (t*n)%inf;
	}
}

void factorial(ll N){
	for(ll i=0;i<=N;i++){
		if(i==0){
			func[i] = 1;
			inv[i] = 1;
		}
		else{
			func[i] = (i*func[i-1])%inf;
			inv[i] = mult(func[i],inf-2);
		}
	}
}

ll comb(ll n,ll k){
    if(n<=0 || k<0) return 0;
	if(k==0 || n==k) return 1;
	else return (((func[n]*inv[k])%inf)*inv[n-k])%inf;
}

ll hcomb(ll n,ll k){
	if(n==0 && k==0) return 1;
	return comb(n+k-1,k);
}

int N,M,D1,D2;
int main(){
    cin >> N >> M >> D1 >> D2;
    factorial(max(N,M));
    ll ans = 0;
	int x = M-1-D1*(N-1);
    for(int i=0;i<=N-1;i++){
		ll r = comb(N-1,i)*comb(x-i*(D2-D1+1)+N,N);
        if(i%2==0) (ans += r)%=inf;
        else (ans += -r+inf)%=inf;
    }
    cout << ans << endl;
}