#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<ll, ll> p_ll;

template<class T>
void debug(T itr1, T itr2) { auto now = itr1; while(now<itr2) { cout << *now << " "; now++; } cout << endl; }
#define repr(i,from,to) for (int i=(int)from; i<(int)to; i++)
#define all(vec) vec.begin(), vec.end()
#define rep(i,N) repr(i,0,N)
#define per(i,N) for (int i=(int)N-1; i>=0; i--)

const ll MOD = pow(10,9)+7;
const ll LLINF = pow(2,61)-1;
const int INF = pow(2,30)-1;

vector<ll> fac;
void c_fac(int x=pow(10,6)+10) { fac.resize(x,true); rep(i,x) fac[i] = i ? (fac[i-1]*i)%MOD : 1; }
ll inv(ll a, ll m=MOD) { ll b = m, x = 1, y = 0; while (b!=0) { int d = a/b; a -= b*d; swap(a,b); x -= y*d; swap(x,y); } return (x+m)%m; }
ll nck(ll n, ll k) { return fac[n]*inv(fac[k]*fac[n-k]%MOD)%MOD; }
ll gcd(ll a, ll b) { if (a<b) swap(a,b); return b==0 ? a : gcd(b, a%b); }
ll lcm(ll a, ll b) { return a/gcd(a,b)*b; }


int main() {
  ll N, M, D1, D2; cin >> N >> M >> D1 >> D2;
  M -= D1 * (N-1) + 1; D2 -= D1;
  // cout << N << " " << M << " " << D2 << endl;

  c_fac(2*pow(10,6)+10);
  if (M<0) { cout << 0 << endl; return 0; }
  ll result = 0, pm = 1;
  rep(i,N) {
    if (M-(D2+1)*i<0) break;
    result = ((result+pm*nck(N-1,i)*nck(N+M-(D2+1)*i, M-(D2+1)*i))%MOD+MOD)%MOD;
    pm *= -1;
    // cout << result << endl;
  }
  cout << result << endl;
  return 0;
}