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.Scanner;

public class perfectperm {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		if(n%2!=0)
		{
			System.out.println(-1);
			return;
		}
		int[] a =new int[n];
		for (int i = 0; i < a.length; i++) {
			a[i] = i+1;
		}
		for (int i = 0; i < a.length; i+=2) {
			int tmp = a[i];
			a[i] = a[i+1];
			a[i+1] = tmp;
		}
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < a.length; i++) {
			if(i!=n && i!=0)
				sb.append(" ");
			sb.append(a[i]);
		}
		System.out.println(sb);
	}
}