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:
//package codechef;

import java.util.*;
import java.io.*;
public class CodeChef
{
    public static int gcd(int a,int b)
    {
        if(b==0) return a;
        return gcd(b,a%b);
    }
    public static int fact(int n)
    {
        int fact = 1;
        for(int i = 1; i<=n; i++) fact*=i;
        return fact;
    }
    public static boolean isPrime(int n)
    {
        for(int i = 2; i<=Math.sqrt(n); i++)
        {
            if(n%i==0)
            {
                return false;
            }
        }
        return true;
    }
    public static void main(String[] args)throws IOException
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String s[] = br.readLine().split(" ");
        int n = Integer.parseInt(s[0]);
        if(n%2==0)
        {
            while(n>0)
            {
                System.out.print(n--+" ");
            }
        }
        else 
        {
            System.out.print("-1");
        }
    }
}