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.*;

public class CF145A{
  public static void main(String args[]) throws IOException {
    BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
    String line = stdin.readLine();
    int n=Integer.parseInt(line);
    
    if(n%2==1){
      System.out.println("-1");
      return;
    }
    
    for(int i=1; i<=n; i+=2){
      System.out.print(i+1);
      System.out.print(" ");
      System.out.print(i);
      if(i!=n) System.out.print(" ");
    }
    
    System.out.println();
  }
}