Optimal Number Permutation

1000ms

262144K

Description:

You have array a that contains all integers from 1 to n twice. You can arbitrary permute any numbers in a.

Let number i be in positions x_i, y_i (x_i < y_i) in the permuted array a. Let's define the value d_i = y_i - x_i — the distance between the positions of the number i. Permute the numbers in array a to minimize the value of the sum $\text{[math]}$ .

Input:

The only line contains integer n (1 ≤ n ≤ 5·10⁵).

Output:

Print 2n integers — the permuted array a that minimizes the value of the sum s.

Sample Input:

Sample Output:

1 1 2 2

Sample Input:

Sample Output:

1 1

Informação

Provedor Codeforces

Código CF622D