Given two integers $N$ and $K$. Your task is to construct an array $A$ such that:

  • $A$ is a permutation with size $N$. (i.e. All $N$ integers from $1$ to $N$ must appear exactly once in $A$)
  • The number of inversions inside $A$ is exactly $K$.

A pair of elements $(A_i, A_j)$ is considered an inversion if and only if $i \lt j$ and $A_i \gt A_j$.

For example, in the array $A=[2, 4, 1, 3]$, there are three pairs of inversion: $(A_1, A_3)$, $(A_2, A_3)$ and $(A_2, A_4)$.

Please note that there might be no valid solution.

Input

The only line contains two integers $N$ and $K$.

Output

If there is no valid solution, output $-1$.

Otherwise, output $N$ integers on a single line, denoting the array $A$. If there are multiple answers, output any of them.

Subtasks

For all test cases, $2 \le N \le 2 \times 10^5$, $0 \le K \le 10^{18}$

Subtask Score Additional Constraints
$1$ $10$ $K = 0$
$2$ $20$ $N \le 10$
$3$ $30$ $K < N$
$4$ $40$ No Additional Constraints

Sample Test Cases

Input Output
4 3 2 4 1 3

This test cases corresponds to the example given in the statement.

5 4 5 1 2 3 4

The four pairs of inversions are $(A_1, A_2)$, $(A_1, A_3)$, $(A_1, A_4)$ and $(A_1, A_5)$.

Click to copy.

Scoring: Per Subtask
Authored by s22f26
Appeared in 2026 Mini Comp 6 (Constructive Algorithms & Special Tasks)