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

public class Della {

    void solve() throws IOException {
        int n = nextInt();
        String sol = "";
        if ( n % 2 != 0 ) {
            out.println("-1");
        }else{
            for ( int i=1; i<=n; i+=2 ){
                sol += i+1 + " " + i + " ";
            }
            out.println(sol.substring(0,sol.length()-1));
        }
    }

    public static void main(String[] args) throws IOException {
        new Della().run();
    }

    StreamTokenizer in;
    PrintWriter out;
    boolean oj = false; //true for defaults IO streams
    BufferedReader br;

    void init() throws IOException {
//      oj = System.getProperty("ONLINE_JUDGE") != null;
        Reader reader = new InputStreamReader(System.in);
        Writer writer = new OutputStreamWriter(System.out);
        br = new BufferedReader(reader);
        in = new StreamTokenizer(br);
        out = new PrintWriter(writer);
    }

    long beginTime;

    void run() throws IOException {
        beginTime = System.currentTimeMillis();
        long beginMem = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
        init();
        solve();
        long endMem = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
        long endTime = System.currentTimeMillis();
//      if (!oj) {
        if (false){
            System.err.println("Memory used = " + (endMem - beginMem));
            System.err.println("Total memory = " + (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory()));
            System.err.println("Running time = " + (endTime - beginTime));
        }
        out.flush();
    }

    int nextInt() throws IOException {
        in.nextToken();
        return (int) in.nval;
    }

    long nextLong() throws IOException {
        in.nextToken();
        return (long) in.nval;
    }

    String nextString() throws IOException {
        in.nextToken();
        return in.sval;
    }

    double nextDouble() throws IOException {
        in.nextToken();
        return in.nval;
    }
}