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:
# https://codeforces.com/problemset/problem/233/A

"""
Permutation - ordered sequence of distinct integers (for the problem a permutation will be size n and all
elements of the permutation are less than or equal to n)

A perfect permutation satisfies forall i <= i <= n:
    p[p[i]] = i
    p[i] != i

Print ANY perfect permutation of size n
If none exists then print -1

If n is odd then it impossible
If n is even you just swap the elements
"""

import sys

n = int(sys.stdin.readline())

if n % 2 != 0:
    sys.stdout.write('-1')
else:
    output = list(range(1,n+1))
    for i in range(n//2):
        output[2*i], output[2*i+1] = output[2*i+1], output[2*i]

    sys.stdout.write(" ".join(map(str, output)))