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 os.path
import math
import heapq
from sys import stdin,stdout
from collections import*
from math import gcd,ceil,floor
mod = int(1e9+7)
##input=sys.stdin.readline
if os.path.exists('Updated prg/Input3d.txt'):
    sys.stdout=open("Updated prg/Output3d.txt","w")
    sys.stdin=open("Updated prg/Input3d.txt","r")
def sinp():return input()
def ninp():return int(sinp())
def mapinp():return map(int,sinp().split())
def linp():return list(mapinp())
def sl():return list(sinp())
def prnt(a):print(a)
n=ninp()
l1=[i for i in range(1,n+1)]
if n%2!=0:
    prnt(-1)
else:
    for i in range(0,n-1,2):
        l1[i],l1[i+1]=l1[i+1],l1[i]
    for i in l1:
        print(i,end=" ")