import java.io.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        long s = sc.nextLong();
        if ((long)n * (n + 1) / 2 < s) {
            System.out.println(-1);
            return;
        }
        Deque<Integer> ans = new ArrayDeque<>();
        long sum = 0;
        for (int i = n; i >= 1; i--) {
            if (sum + i > s) {
                break;
            }
            sum += i;
            ans.addFirst(i);
        } 
        if (sum < s) {
            ans.addFirst((int)(s - sum));
        }
        System.out.println(ans.size());
        System.out.println(ans.stream().map(x -> x.toString()).collect(Collectors.joining(" ")));
    }
}
class Scanner {
    BufferedReader br;
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            
        }
    }
    
    public int nextInt() {
        return Integer.parseInt(next());
    }
    
    public long nextLong() {
        return Long.parseLong(next());
    }
    
    public double nextDouble() {
        return Double.parseDouble(next());
    }
    
    public String next() {
        try {
            while (!st.hasMoreTokens()) {
                st = new StringTokenizer(br.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            return st.nextToken();
        }
    }
    
}