human
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 
Solve the task in PYTHON.
assistant
#Here is Python code to print any perfect permutation of size n for the given n.

class PerfectPermutation:
    def solve(self, n):
        count = n
        if n==1 or n%2!=0:
            print -1
            return
        arr = []
        for x in range(1, n + 1):
            arr.append(x)
        index = 0
        while index < count-1:
            if index%2==0:
                temp = arr[index]
                arr[index]=arr[index+1]
                arr[index+1]=temp
            index+=1
        for x in arr:
            print x,

if __name__ == "__main__":
    n = int(raw_input())
    pp = PerfectPermutation()
    pp.solve(n)