Perfect Permutation

2000ms

262144K

Description:

A permutation is a sequence of integers p₁, p₂, ..., p_n, consisting of n distinct positive integers, each of them doesn't exceed n. Let's denote the i-th element of permutation p as p_i. We'll call number n the size of permutation p₁, p₂, ..., p_n.

Nickolas adores permutations. He likes some permutations more than the others. He calls such permutations perfect. A perfect permutation is such permutation p that for any i (1 ≤ i ≤ n) (n is the permutation size) the following equations hold p_{p_i} = i and p_i ≠ i. Nickolas asks you to print any perfect permutation of size n for the given n.

Input:

A single line contains a single integer n (1 ≤ n ≤ 100) — the permutation size.

Output:

If a perfect permutation of size n doesn't exist, print a single integer -1. Otherwise print n distinct integers from 1 to n, p₁, p₂, ..., p_n — permutation p, that is perfect. Separate printed numbers by whitespaces.

Sample Input:

Sample Output:

-1

Sample Input:

Sample Output:

2 1

Sample Input:

Sample Output:

2 1 4 3

Informação

Provedor Codeforces

Código CF233A