CF233A.Perfect Permutation

A permutation is a sequence of integers $p_{1},p_{2},...,p_{n}$ , 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 $p_{1},p_{2},...,p_{n}$ .

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 $p_{pi}=i$ and $p_{i}≠i$ . Nickolas asks you to print any perfect permutation of size $n$ for the given $n$ .

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

If a perfect permutation of size $n$ doesn't exist, print a single integer -1. Otherwise print $n$ distinct integers from 1 to $n$ , $p_{1},p_{2},...,p_{n}$ — permutation $p$ , that is perfect. Separate printed numbers by whitespaces.