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>
bool isvowel(char s) {
  if (s == 'a' || s == 'A' || s == 'e' || s == 'E' || s == 'i' || s == 'I' ||
      s == 'o' || s == 'O' || s == 'u' || s == 'U')
    return true;
  else
    return false;
}
long long fact(long long n) {
  long long mul = 1;
  for (long long i = 1; i <= n; i++) mul = mul * i;
  return mul;
}
long long gcd(long long a, long long b) {
  return b == 0 ? a : gcd(b % 1000000007, (a % b) % 1000000007);
}
using namespace std;
int main() {
  int n;
  cin >> n;
  if (n & 1)
    cout << "-1"
         << "\n";
  else {
    for (int i = 1; i <= n; i += 2) {
      cout << i + 1 << " " << i << " ";
    }
  }
  return 0;
}