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.io.*;
import java.util.*;

public class Main{
    public static String getString() throws Exception{
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String str=br.readLine();
        
        return str;
    }
    public static int getInt() throws Exception{
        String str=getString();
        return Integer.parseInt(str);
    }
    public static void main(String args[]) throws Exception{
        int n=getInt();
        if(n%2==1){
            System.out.print("-1");
        }
        else{
            for(int i=1;i<=n;i+=2){
                System.out.print(i+1 + " " + i + " ");
            }
        }
        System.out.println();
    }
    
}