#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <utility>
#include <functional>
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
const ll MOD=1e9+7;
ll powmod(ll a, ll k){
    ll ap=a, ans=1;
    while(k){
        if(k&1){
            ans*=ap;
            ans%=MOD;
        }
        ap=ap*ap;
        ap%=MOD;
        k>>=1;
    }
    return ans;
}
ll inv(ll a){
	return powmod(a, MOD-2);
}
ll f[1500001], invf[1500001];
void fac(int n){
    f[0]=1;
    for(ll i=1; i<=n; i++) f[i]=f[i-1]*i%MOD;
    invf[n]=inv(f[n]);
    for(ll i=n-1; i>=0; i--) invf[i]=invf[i+1]*(i+1)%MOD;
}
ll comb(int x, int y){
    if(x<y) return 0;
    return f[x]*invf[y]%MOD*invf[x-y]%MOD;
}
int main()
{
    int n, m, d1, d2; cin>>n>>m>>d1>>d2;
    if((ll)(m-1)<(ll)d1*(ll)(n-1)){
        cout<<0<<endl;
        return 0;
    }
    m-=d1*(n-1);
    d2-=d1;
    fac(n+m);
    ll ct[300001];
    for(int i=0; i<n; i++){
        if((ll)i*(ll)(d2+1)>=(ll)m){
            ct[i]=0; continue;
        }
        ll m1=m-1-(d2+1)*i;
        ct[i]=comb(n-1, i)*comb(m1+n, n)%MOD;
    }
    ll ans=0;
    for(int i=0; i<n; i++){
        if(i&1) ans+=(MOD-ct[i]);
        else ans+=ct[i];
        ans%=MOD;
    }
    cout<<ans<<endl;
    return 0;
}