package net.ipipip0129.yukicoder.no598;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        long bit_len = Long.parseLong(scan.nextLine());
        long enemy_hp = Long.parseLong(scan.nextLine());
        long attack_point = Long.parseLong(scan.nextLine());
        long heal_point = Long.parseLong(scan.nextLine());

        long overflow_point = (long) (Math.pow(2,bit_len - 1) - enemy_hp);

        long attack_cnt = enemy_hp / attack_point;
        if (enemy_hp % attack_point != 0) attack_cnt += 1;

        long heal_cnt = overflow_point / heal_point;
        if (overflow_point % heal_point != 0) heal_cnt += 1;

        System.out.println(Math.min(attack_cnt, heal_cnt));
    }
}