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.*;
import java.math.*;

public class practice {
    public static void main(String[] args) throws Exception {
        Scanner in = new Scanner(System.in);
        
        int a = Integer.parseInt(in.nextLine());
        
        if(a % 2 == 0) {
            for(int i = 0; i < a / 2 - 1; i++) {
                System.out.print((2 * i + 2) + " " + (2 * i + 1) + " ");
            }
            System.out.println(a + " " + (a - 1));
        } else {
            System.out.println(-1);
        }
    }
}