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

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 ppi = i and pi ≠ 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, ..., pn — permutation p, that is perfect. Separate printed numbers by whitespaces.

Examples

Input

1


Output

-1


Input

2


Output

2 1 


Input

4


Output

2 1 4 3 

Solution (in JAVA):

Solution:
import java.util.*;

public class PerfectPermutation {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n;
        n = in.nextInt();

        if (n > 0 && n % 2 == 0) {
            for (int i = 1; i <= n; i++) {
                if (i % 2 != 0)
                    System.out.print(i + 1 + " ");
                else
                    System.out.print(i - 1 + " ");
            }
        }
        else
            System.out.print("-1");

        in.close();
    }

}