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.Scanner;

public class UpperCase {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
       int num;
       int j;
       num=input.nextInt();
       if(num%2!=0)
           System.out.println(-1);
       else
           for(int i=1;i<=num;i++)
           {
               j=i;
               if(j%2!=0)
               {   j++;
                   System.out.print(j+" ");
               
               }
               else
               {j--;
                   System.out.print(j+" ");}
               
           }
           System.out.println();
        }
    }// main