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.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StreamTokenizer;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

public class A {

	public static void main(String[] args) throws IOException {
		int n = i();
		int i = 1;
		if ((n & 1) != 0){
			pw.println(-1);
		}else{
			while (i<n){
				pw.print((i+1) + " " + i + " ");
				i+=2;
			}
		}
		pw.close();
	}

	// -- DEBUG switch --
	static final boolean DBG = false;
	static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	static StreamTokenizer st = new StreamTokenizer(br);
	static PrintWriter pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
	
	static int i() throws IOException{
		st.nextToken();
		return (int)st.nval;
	}
	
	static long l() throws IOException {
		st.nextToken();
		return (long)st.nval;
	}

	static double d() throws IOException {
		st.nextToken();
		return st.nval;
	}
	static String s() throws IOException{
		st.nextToken();
		return st.sval;
	}
}