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:
/******************************************************************************

                            Online Java Compiler.
                Code, Compile, Run and Debug java program online.
Write your code in this editor and press "Run" button to execute it.

*******************************************************************************/
import java.util.*;
public class Main
{
	public static void main(String[] args) {
	
	    Scanner sc=new Scanner(System.in);
	    int n=sc.nextInt();
	    if(n%2!=0)
	    System.out.println(-1);
	    else
	    {
	        int arr[]=new int[101];
	        int i;
	        for(i=1;i<=n;i++)
	        {
	            if(i%2!=0)
	            {
	                arr[i]=i+1;
	            }
	            else
	            {
	                arr[i]=i-1;
	            }
	        }
	        for(i=1;i<=n;i++)
	        System.out.print(arr[i]+" ");
	    }
	    sc.close();
	}
	
}