#include <iostream>
#include <atcoder/modint>

using namespace std;
using namespace atcoder;
using mint = modint1000000007;
using ll = long long;
const int MX = 2000010;
mint f[MX],inv[MX],fi[MX];
constexpr ll mod = 1000000007;
void solve(){
    inv[1] = 1;
    for(int i=2;i<MX;i++){
        inv[i] = mod - (mod/i)*inv[mod%i];
    }
    f[0] = fi[0] = 1;
    for(int i=1;i<MX;i++){
        f[i] = f[i-1]*i;
        fi[i] = fi[i-1]*inv[i];
    }
}

mint nck(ll n, ll k){
    if(n<0 || k<0 || n<k) return 0;
    return f[n]*fi[k]*fi[n-k];
}

int main(){
    ll n,m,d1,d2; cin >> n >> m >> d1 >> d2;
    solve();
    mint ans = 0;
    for(int i=0;i<n;i++){
        mint val = nck(n - 1,i)*nck(n + m - d1*(n - 1) - 1 - i*(d2 - d1 + 1),n);
        if(i&1) ans -= val;
        else ans += val;
    }
    cout << ans.val() << "\n";
}