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 com.sun.security.jgss.GSSUtil;

        import java.io.*;
        import java.lang.reflect.Array;
import java.math.BigInteger;
import java.nio.Buffer;
        import java.util.*;
        import java.io.BufferedReader;
        import java.io.InputStreamReader;
        import java.io.IOException;

public class Pair {


    public static void main(String[] args) throws Exception {
        try {
            Scanner sc = new Scanner(System.in);
            int n = sc.nextInt();
            if(n%2==0){
                for(int i=1;i<=n/2;i++){
                    System.out.print((i*2)+" "+(i*2-1)+" ");
                }
            }
            else{
                System.out.println(-1);
            }

        }
        catch (Exception e) {
        }
    }
}