import java.util.*;

class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n=scan.nextInt();
        long x=scan.nextLong();
        long a=scan.nextLong();
        long b=scan.nextLong();
        long mi=(x+a-1)/a;
        mi=Math.min(mi,((1<<(n-1))-x+b-1)/b);
        System.out.println(mi);
    }
}