#include <bits/stdc++.h>
using namespace std;
typedef long long ll; 
const ll mod = 1000000007;

ll qp(ll a, ll b, ll c) {
    a %= c;
    ll r = 1;
    while (b) {
        if (b & 1) r = r * a % c;
        a = a * a % c;
        b >>= 1;
    }
    return r;
}

int main() {
    ll n, m, d1, d2;
    cin >> n >> m >> d1 >> d2;
    if (n == 1) {
        cout << m % mod << endl;
        return 0;
    }
    if (m - 1 < (n - 1) * d1) {
        cout << 0 << endl;
        return 0;
    }
    if (d2 < d1) {
        cout << 0 << endl;
        return 0;
    }
    ll x = 2LL * m - (n - 1) * (d1 + d2);
    x %= mod;
    if (x < 0) x += mod;
    ll b = d2 - d1 + 1;
    ll p = qp(b, n - 1, mod);
    ll i2 = (mod + 1) / 2;
    ll a = x * p % mod;
    a = a * i2 % mod;
    cout << a << endl;
    return 0;
}