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:
/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */


import java.io.IOException;

/**
 *
 * @author wijebandara
 */
public class Main {
    public static void main(String[] args)throws IOException
    {
        java.io.BufferedReader in =new java.io.BufferedReader(new java.io.InputStreamReader(System.in));
        
        
        int n = Integer.parseInt(in.readLine());
        
        if(n%2==0)
        {
            for(int i=1;i<=n;i+=2)
            {
                System.out.print((i+1)+" "+i+ " ");
                
            }
            System.out.println("");
        }
        else 
        {
            System.out.println("-1");
        }
        
    }
    
}