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:

"""
Created on Mon Jul  6 21:28:12 2020

@author: rishi
"""
import math

def sumofno(n):
    summ=0
    while(n>0):
        summ+=n%10
        n//=10
    return summ

def get_key(val,lis): 
    for key, value in lis.items(): 
         if value == val : 
             return key 

def isprime(val):
    c=0
    for j in range(2,val):
        if(val%j)==0:
            return False
    return True
            
#print(isprime(15))
try:
    #t=int(input())
    ans=[]
    
    for i in range(1):
        n=int(input())
        if(n%2!=0):
            ans.append(-1)
            break
        else:
            m=n//2
            ann=""
            for j in range(m):
                j1=j+1
                
                ann+=str(2*j1)
                ann+=" "
                ann+=str((2*j1)-1)
                ann+=" "
            ans.append(ann)
                
                
                    
                
                
                
                
        
    #print (ans)
    for an in ans:
        #print("hi")
        print(an)

except:
    pass