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.io.*;

public class MainApp
{
    public static void main(String[] args) throws IOException {
        FastScanner fs = new FastScanner();
        int n = fs.nextInt();

        if(n % 2 == 1)
            System.out.println(-1);
        else
            for (int i = 0; i < n;) {
                System.out.printf("%d %d ", i+2, i+1);
                i+=2;
            }
    }
}

class FastScanner
{
    private BufferedReader bf;
    private StringTokenizer st;

    public FastScanner()
    {
        bf = new BufferedReader(new InputStreamReader(System.in));
        st = null;
    }

    public String next()
    {
        while (st == null || !st.hasMoreTokens())
        {
            try
            {
                st = new StringTokenizer(bf.readLine());
            }
            catch (IOException e)
            {
                throw new RuntimeException(e);
            }
        }
        return st.nextToken();
    }

    public int nextInt()
    {
        return Integer.parseInt(this.next());
    }
    public long nextLong() { return Long.parseLong(this.next()); }
}