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 CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
char a[100000];
struct asa {
  int a, b;
} ko[100000];
bool cmp(asa a, asa b) { return a.a < b.a; }
int h[9000], s[1000], dp[500][50000][2];
int main() {
  int n;
  cin >> n;
  if (n & 1)
    cout << -1 << endl;
  else {
    for (int i = 1; i <= n / 2; i++) {
      cout << 2 * i << " " << 2 * i - 1 << ' ';
    }
    cout << endl;
  }
}