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.
 */
//package javaapplication1;

import java.awt.List;
import java.util.Scanner;
import java.math.MathContext;
import java.math.BigInteger;

/**
 *
 * @author Ghazale
 */
public class JavaApplication1 {

    /**
     * @param args the command line arguments
     */
    public static double mymin;

    public static boolean isPrime(int a) {
        if (a <= 1) {
            return false;
        }
        if (a == 2) {
            return true;
        }
        for (int i = 2; i <= Math.sqrt(a) + 1; i++) {
            if (a % i == 0) {
                return false;
            }

        }
        return true;
    }

    public static double function(int n) {
        double sum = 0;
        if (n == 1) {
            return 0;
        }
        for (int i = 2; i < n / 2 + 1; i++) {
            if (n % i == 0) {
                sum += n / i + i;
            }
        }
        return (sum + 1) / n;
    }

    public static void main(String[] args) {
        // TODO code application logic here
        //Scanner f = new Scanner("src\\input.txt");

        Scanner f = new Scanner(System.in);
        double mymin = 10001;
        int N = f.nextInt();
        int array[] = new int[N+1];
        if(N%2==1)
            System.out.println("-1");
        else{
            for (int i = 1; i <= N; i++) {
                if(i%2==1){
                   array[i] =  i+1;
                }else{
                    array[i] = i-1;
                }
                
            }
            for (int i = 1; i <= N; i++) {
                System.out.print(array[i]+" ");
            }
            
        }
        
    }
}