using System.Collections.Generic;

using static System.Console;
using static System.Linq.Enumerable;

var (N, S) = Util.ReadLongs();

List<long> ans = new();
HashSet<long> visited = new();

bool Search(long n, long s)
{
	if (n == 0) return s == 0;
	if (s < 0) return false;

	if (!visited.Add(N * s + n)) return false;

	if (Search(n - 1, s - n)) {
		ans.Add(n);
		return true;
	}

	return Search(n - 1, s);
}

if (Search(N, S)) {
	WriteLine(ans.Count);
	WriteLine(string.Join(' ', ans));
}
else {
	WriteLine("Impossible");
}

static class Util
{
	public static int[] ReadInts() => ReadLine()!.Split().Select(int.Parse).ToArray();
	public static long[] ReadLongs() => ReadLine()!.Split().Select(long.Parse).ToArray();
	public static void Deconstruct<T>(this T[] v, out T a, out T b) { a = v[0]; b = v[1]; }
}