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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Scanner;


public class A {

	
	public static void main(String[] args) throws IOException {
//		BufferedReader reader = new BufferedReader(new InputStreamReader(
//				System.in));
		Scanner sc = new Scanner(System.in);
		int k = sc.nextInt();
		if((k&1)!=0)
		{
			System.out.println(-1);
		}
		else
		{
			int a[]=new int [k+1];
			for(int i=1;i<k;i+=2)
			{
				a[i]=i+1;
				a[i+1]=i;
			}
			for(int i=1;i<a.length-1;i++)
				System.out.print(a[i]+" ");
			System.out.println(a[a.length-1]);
		}
	}

}