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:
#n, d = input().split()
#n = int (n)
#d = int (d)
n = int(input())
#a = list(map(int, input().split()))
#g = list(map(int, input().split()))
#x1, y1, x2, y2 =map(int,input().split())
#n = int(input())
# = [""]*n
#f = [0]*n
#t = [0]*n
#f = []

#h = [""] * n
#f1 = sorted(f, key = lambda tup: tup[0])
s = ""
if (n % 2== 1):
    print(-1)

else:
    for i in range (1, n+1):
        if (i % 2 == 1):
            s += str(i+1)+" "
        else:
            s += str(i-1)+" "
    print (s)