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:
import sys
import math
import collections
from collections import deque

#sys.stdin = open('input.txt', 'r')
#sys.stdout = open('output.txt', 'w')

from functools import reduce
from sys import stdin, stdout, setrecursionlimit
setrecursionlimit(2**20)


def factors(n):
    return list(set(reduce(list.__add__,
                           ([i, n // i] for i in range(1, int(n**0.5) + 1) if n % i == 0))))


def isPrime(n):
    # Corner cases
    if (n <= 1):
        return False
    if (n <= 3):
        return True

    # This is checked so that we can skip
    # middle five numbers in below loop
    if (n % 2 == 0 or n % 3 == 0):
        return False

    i = 5
    while(i * i <= n):
        if (n % i == 0 or n % (i + 2) == 0):
            return False
        i = i + 6
    return True

# for _ in range(int(stdin.readline())):
n = int(stdin.readline().strip('\n'))
#b = str(stdin.readline().strip('\n'))
#a = list(map(int, stdin.readline().split()))
#n, m = list(map(int, stdin.readline().split()))
#s = list(str(stdin.readline().strip('\n')))
#n = len(a)
if n % 2 == 0:
    for i in range(1, (n) // 2 + 1):
        print(2 * i, 2 * i - 1, end=" ")
else:
    print(-1)