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 PYTHON3):

Solution:
'''
##======================================================================================================================================##
   ##         _____       _       _    _    _____   _      _  _    _   _____          _____    ____       ___     ____   ___         ##
      ##     |           / \     | \  / |  |        |      |  |\   |  |     |        |        |    |  |  |   \   |      |   |     ##
         ##  |_____     /   \    |  \/  |  |_____   |      |  | \  |  |    __   ---  |_____   |____|  |  |    |  |___   |___|  ##
      ##           |   /     \   |      |        |  |      |  |  \ |  |     |              |  |       |  |    |  |      |  \      ##
   ##         _____|  /       \  |      |   _____|   \ __ /   |   \|  |_____|         _____|  |       |  |___/   |____  |   \        ##
##======================================================================================================================================##
------------------------------Samsung_Spider------------------------------
'''
n = int(input()); f = 2; s = 1
if n % 2 != 0:
    print("-1")
else:
    while n > 0:
        print(f, s, end = " ")
        f += 2
        s += 2
        n -= 2