|Educational Codeforces Round 7|
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 xi, yi (xi < yi) in the permuted array a. Let's define the value di = yi - xi — the distance between the positions of the number i. Permute the numbers in array a to minimize the value of the sum .
The only line contains integer n (1 ≤ n ≤ 5·105).
Print 2n integers — the permuted array a that minimizes the value of the sum s.
1 1 2 2