#include <bits/stdc++.h>
#define REP(i, x, y) for (ll i = x; i <= y; i++)
#define BIT(t) (1ll << t)
#define PER(i, y, x) for (ll i = y; i >= x; i--)
#define vll vector<ll>
#define vvll vector<vector<ll>>
#define pll pair<ll, ll>
#define SIZE(v) ll(v.size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());
using namespace std;
typedef long long ll;
//        ios::sync_with_stdio(false);
//        cin.tie(nullptr);

ll const MOD = 1e9 + 7;
ll mod_p(ll x, ll y) {
       x %= MOD;
       y %= MOD;
       return (x + y + MOD) % MOD;
}

ll mod_m(ll x, ll y) {
       x %= MOD;
       y %= MOD;
       return x * y%MOD;
}

ll mod_pow(ll x, ll t) {
       x %= MOD;
       if (t == 0) {
               return 1;
       }
       else {
               ll v = mod_pow(x, t / 2);
               if (t % 2 == 0) {
                       return v * v % MOD;
               }
               else {
                       return v * v%MOD * x %MOD;
               }
       }
}

ll mod_inv(ll x) {
       return mod_pow(x, MOD - 2);
}

vll fct(2e6+1), invfct(2e6+1);
void init(){
        fct[0] = invfct[0] = 1;
        REP(i,1,2e6){
                fct[i] = mod_m(fct[i-1] , i);
                invfct[i] = mod_inv(fct[i]);
        }
}

ll ncr(ll n, ll r){
        return mod_m(fct[n], mod_m(invfct[r], invfct[n-r]));
}

int main(){
        init();
        ll n,m,d1, d2;
        cin >> n >> m >> d1 >> d2;
        ll d = d2 - d1;
        ll l = m - 1 - d1*(n-1);
        if(l < 0){
                cout << 0 << endl;
                return 0;
        }
        vll a(m+2), sm(m+2,0);
        REP(i,0,m){
                a[i] = ncr(n+i-1, i);
        }
        sm[0] = a[0];
        REP(i,1,m){
                sm[i] = mod_p(sm[i-1],a[i]);
        }
        ll ans = 0;
        REP(i,0,n-1){
                ll  tmp = ncr(n-1, i);
                if(i % 2 == 1){
                        tmp = mod_m(tmp, -1);
                }
                ll v = l - i * (d + 1);
                if(v < 0) break;
                ans = mod_p(ans, mod_m(sm[v], tmp));
               // cout << v << " " << mod_m(sm[v], tmp) << endl;
        }
        cout << ans << endl;
}