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.*;
import java.io.*;

public class A144
       {
       public static void main(String args[]) throws IOException
               {
               BufferedReader c=new BufferedReader(new InputStreamReader(System.in));
               //Scanner c=new Scanner(System.in);
//                int n=c.nextInt();
               
//                String s=c.readLine();;
//                StringTokenizer st = new StringTokenizer(s);
//                int n=Integer.parseInt(st.nextToken());
               
               
               
               int n=Integer.parseInt(c.readLine());
               if(n%2==1)
                       {
                       System.out.println(-1);
                       return;
                       }
               
               for(int t=1;t<=n;t=t+2)
                       {
                       System.out.print((t+1)+" "+t+" ");
                       }
               }
       }

//must declare new classes here