CodeForces 233A Perfect Permutation

A. Perfect Permutation

time limit per test

2 seconds

memory limit per test

256 megabytes

input

standard input

output

standard output

A permutation is a sequence of integers p₁, p₂, ..., p_n, consisting of n distinct positive integers, each of them doesn't exceed n. Let's denote the i-th element of permutation p as p_i. We'll call number n the size of permutation p₁, p₂, ..., p_n.

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 p_pi = i and p_i ≠ 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, ..., p_n — 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 

#include<iostream>                            
#include<algorithm>                                                       
using namespace std;                          
                                              
int main(){                                   
	int n,i,d;                                         
	while(cin>>n){  
		if(n%2){
			cout<<"-1"<<endl;
		}            
		else{
			d=n-2;
			for(i=0;i<n;i+=2){
				if(i==d){
					cout<<i+2<<" "<<i+1<<endl;
				}
				else{
					cout<<i+2<<" "<<i+1;
					cout<<" ";
				}
				
			}  
		}                                        
	}                                            
	return 0;                                    
}