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 PYTHON):

Solution:
####################################################
# -*- coding: utf-8 -*-
import sys

w = sys.stdout.write
read = sys.stdin.readline
reads = sys.stdin.read

def r(f=None):
    if f:
        return map(f, read().split())
    else:
        return read().split()

def rs(t,f=None):
    result = []
    result_append = result.append
    for i in xrange(t):
        if f:
            result_append(map(f, read().split()))
        else:
            result_append(read().split())
    return result


####################################################
import math

[n] = r(int)

if n % 2 == 1:
    w('-1')
else:
    w(" ".join(["%s %s" % (i+2, i+1) for i in range(0, n, 2)]))