MOD = 10**9 + 7

def main():
    import sys
    input = sys.stdin.read
    data = input().split()
    N = int(data[0])
    M = int(data[1])
    D1 = int(data[2])
    D2 = int(data[3])
    n = N - 1
    S_low = n * D1
    S_high = min(n * D2, M - 1)
    
    if S_low > S_high:
        print(0)
        return
    
    T_max = S_high - S_low
    c = D2 - D1
    
    if c == 0:
        print((M - S_low) % MOD)
        return
    
    max_fact = T_max + n + (n - 1) + 2
    max_fact = min(max_fact, 2 * 10**6)
    
    fact = [1] * (max_fact + 1)
    for i in range(1, max_fact + 1):
        fact[i] = fact[i - 1] * i % MOD
    
    inv_fact = [1] * (max_fact + 1)
    inv_fact[max_fact] = pow(fact[max_fact], MOD - 2, MOD)
    for i in range(max_fact - 1, -1, -1):
        inv_fact[i] = inv_fact[i + 1] * (i + 1) % MOD
    
    def comb(a, b):
        if a < 0 or b < 0 or a < b:
            return 0
        return fact[a] * inv_fact[b] % MOD * inv_fact[a - b] % MOD
    
    sum_A = 0
    max_k = (T_max + n) // (c + 1)
    for k in range(0, max_k + 1):
        rem = T_max + n - k * (c + 1)
        if rem < 0:
            continue
        term_n_k = comb(n, k)
        term_comb = comb(rem, n)
        term = term_n_k * term_comb % MOD
        if k % 2 == 1:
            term = (-term) % MOD
        sum_A = (sum_A + term) % MOD
    
    sum_B = 0
    e_max = min(c, T_max)
    for e in range(0, e_max + 1):
        current_T = T_max - e
        if current_T < 0:
            break
        temp_sum = 0
        max_k_current = (current_T + (n - 1)) // (c + 1)
        for k in range(0, max_k_current + 1):
            rem = current_T + (n - 1) - k * (c + 1)
            if rem < 0:
                continue
            term_n_1_k = comb(n - 1, k)
            term_comb = comb(rem, n - 1)
            term = term_n_1_k * term_comb % MOD
            if k % 2 == 1:
                term = (-term) % MOD
            temp_sum = (temp_sum + term) % MOD
        sum_B = (sum_B + e * temp_sum) % MOD
    sum_B = sum_B * n % MOD
    
    answer = ((M - S_low) * sum_A - sum_B) % MOD
    if answer < 0:
        answer += MOD
    print(answer)

if __name__ == "__main__":
    main()