B - The Child and Set

B - The Child and Set

import java.util.*;
import java.lang.*;
public class Main{
	public static void main(String args[])
	{
		Scanner in=new Scanner(System.in);
		int sum=in.nextInt();
		int limit=in.nextInt();
		int mask=0,size=0;
		StringBuffer sb=new StringBuffer();
		for(int i=limit;i>0;i--)
		{
			int bit=Integer.lowestOneBit(i);
			if(bit+mask<=sum)
			{
				size+=1;
				mask+=bit;
				sb.append(i + " ");
			}
		}
		if(mask!=sum)
			System.out.println(-1);
		else
		{
			System.out.println(size);
			System.out.println(sb);
		}
	}
}