## Algorithm

A. Perfect Permutation
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

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 np1, p2, ..., pn — permutation p, that is perfect. Separate printed numbers by whitespaces.

Examples
input
Copy
`1`
output
Copy
`-1`
input
Copy
`2`
output
Copy
`2 1 `
input
Copy
`4`
output
Copy
`2 1 4 3 `

## Code Examples

### #1 Code Example with C++ Programming

```Code - C++ Programming```

``````#include <bits/stdc++.h>

using namespace std;

int main() {
int n;
scanf("%d", &n);

if(n & 1) {
puts("-1");
return 0;
}

for(int i = 0; i < n; i += 2)
printf("%d %d ", i + 2, i + 1);
puts("");

return 0;
}``````
Copy The Code &

Input

cmd
1

Output

cmd
-1