def main():
    N, X, A, B = (int(input()) for _ in [0] * 4)

    attack = (X + A - 1) // A
    bin_ = '1' + '0' * (N - 1)
    overflow = int(bin_, 2)
    recovery = (overflow - X + B - 1) // B

    print(min(attack, recovery))

main()