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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class ProblemA {
    public static void main(String[] args) throws IOException {
        BufferedReader s = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);
        int n = Integer.valueOf(s.readLine());
        
        StringBuffer answer = new StringBuffer();

        if (n % 2 == 0) {
            for (int i = 0 ; i < n / 2 ; i++) {
                if (i >= 1) {
                    answer.append(" ");
                }
                answer.append(i*2+2).append(" ").append(i*2+1);
            }
        } else {
            answer.append("-1");
        }
        
        out.println(answer.toString());
        
        out.flush();
    }

    public static void debug(Object... os){
        System.err.println(Arrays.deepToString(os));
    }
}