#include <bits/stdc++.h>
using namespace std;
using PP = pair<long, long>;
const int INF = 1e9;
template <class T> T Next() { T t; cin >> t; return t; }

const long mod = 1000000007;

long powmod(long b, long e) {
  if (e == 0) return 1;
  if (e % 2 == 1) return powmod(b, e - 1) * b % mod;
  long t = powmod(b, e / 2);
  return t * t % mod;
}

long inv(long n) {
  return powmod(n, mod - 2);
}

long f[2000001];
long combi(long n, long r) {
  if (r < 0 || r > n) return 0;
  return f[n] * inv(f[r] * f[n - r] % mod) % mod;
}

long hcombi(long n, long r) {
  if (r < 0) return 0;
  return combi(n + r - 1, r);
}

long p[1000001];
long q[1000001];
void pre(long n, long m) {
  f[0] = 1;
  for (long i = 1; i <= n + m; ++i) {
    f[i] = f[i - 1] * i % mod;
  }
  
  for (long i = 0; i < max(n, m); ++i) {
    p[i + 1] = (p[i] + hcombi(n, i)) % mod;
    q[i + 1] = (q[i] + i * hcombi(n, i) % mod) % mod;
  }
}

long sub(long n, long m, long l) {
  pre(n, m);
  
  long sum = 0;
  for (long k = 0; k <= min(n, m); ++k) {
    long s = m - l * k;
    if (s < 0) continue;
    long a = s * p[s] % mod;
    long b = q[s];
    long c = (a + mod - b) % mod;
    long d = k % 2 == 0 ? 1 : mod - 1;
    long e = combi(n, k) * c % mod * d % mod;
    sum = (sum + e) % mod;
  }
  return sum;
}

int main() {
  long n, m, a, b;
  cin >> n >> m >> a >> b;
  cout << sub(n - 1, m - a * (n - 1), b - a + 1) << endl;
  return 0;
}