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
import sys
#-----------------------------------------------------------------------------#
try:
    sys.stdin = open('inputs.txt', 'r')
    sys.stdout = open('output.txt', 'w')
except:
    pass
finally:
    input = sys.stdin.readline
    print = sys.stdout.write

#-----------------------------------------------------------------------------#

n = int(input())

if n & 1:
    print(str(-1))

else:
    out = [str(i + 1) if i & 1 else str(i - 1) for i in range(1, n + 1)]
    print(" ".join(out))