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;

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



//********************************************************K.S.J _@@@@@@@@@@@@@@@@@@@@@@@@@******************************
public class permute{
	static BufferedReader reader;
    static StringTokenizer tokenizer;
	
	static void init(InputStream input) {reader = new BufferedReader(new InputStreamReader(input) );
        tokenizer = new StringTokenizer("");
    }
	static String next() throws IOException {
        while (!tokenizer.hasMoreTokens() ) { tokenizer = new StringTokenizer(reader.readLine() );}
        return tokenizer.nextToken();
    }
	static String nextLine() throws IOException { return  next();}
	static int nextInt() throws IOException {return Integer.parseInt( next() );}
	static double nextDouble() throws IOException {return Double.parseDouble( next() );}
	static long nextLong() throws IOException {return Long.parseLong( next() );}
	static BigInteger nextBigInteger() throws IOException {return new BigInteger(next()) ;}


	
	
	   
	


	public static void main(String args[]) throws IOException{
		init(System.in);                                                                                                                                                                    
		
		int no=nextInt();
		int arr[]=new int[no+1];
		if(no%2==0){
			for(int i=1;i<=no;i++){
				if(i%2==0){
					arr[i]=i-1;
				}
				else{
					arr[i]=i+1;
				}
			}
			for(int i=1;i<=no;i++){
				System.out.print(arr[i]+" ");
				}
		}
		else{
			System.out.println("-1");
		}

	}

}