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:
import bisect
from collections import defaultdict
from collections import deque
import math
import re
import sys
import itertools

def ni():
    return int(raw_input())

def nis():
    return map(int, raw_input().split())

def si():
    return raw_input()

def sis():
    return raw_input().split()

def spaced(a):
    return ' '.join(map(str, a))

n = ni()

if n % 2:
    print -1
else:
    a = range(1, n + 1)
    for i in range(0, n - 1, 2):
        a[i], a[i + 1] = a[i + 1], a[i]

    print spaced(a)