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.*;
import java.io.*;

public class A233 implements Runnable{
	
	public void solve() throws IOException{
		int N = nextInt();
		if(N % 2 == 1) System.out.println(-1);
		else{
			int[] a = new int[N];
			for(int i = 0; i < N; i += 2){
				a[i] = i + 2;
				a[i + 1] = i + 1;
			}
			
			for(int i = 0; i < N; i++){
				System.out.print(a[i]);
				if(i != N -1) System.out.print(" ");
			}
			System.out.println();
		}
	}
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	//$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
	public static void main(String[] args){
		new A233().run();
	}
	
	public void run(){
		try{
			in = new BufferedReader(new InputStreamReader(System.in));
			tok = null;
			solve();
			in.close();
		}
		catch(IOException e){
			System.exit(0);
		}
	}
	
	public String nextToken() throws IOException{
		while(tok == null || ! tok.hasMoreTokens()){
			tok = new StringTokenizer(in.readLine());
		}
		return tok.nextToken();
	}
	
	public int nextInt() throws IOException{
		return Integer.parseInt(nextToken());
	}
	
	public long nextLong() throws IOException{
		return Long.parseLong(nextToken());
	}
	
	public double nextDouble() throws IOException{
		return Double.parseDouble(nextToken());
	}
	
	BufferedReader in;
	StringTokenizer tok;
	
}