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;
const long long int mod = 1e9 + 7;
inline long long int add(long long int a, long long int b) {
  return (a % mod + b % mod) % mod;
}
inline long long int sub(long long int a, long long int b) {
  return (a % mod - b % mod + mod) % mod;
}
inline long long int mul(long long int a, long long int b) {
  a %= mod;
  b %= mod;
  return a * b % mod;
}
inline long long int power(long long int a, long long int b,
                           long long int MOD) {
  a %= mod;
  long long int res = 1;
  while (b) {
    if (b & 1) {
      res *= a;
      res %= MOD;
    }
    a = a * a;
    a %= MOD;
    b >>= 1;
  }
  return res;
}
clock_t time_p = clock();
void time() {
  time_p = clock() - time_p;
  cerr << "Time elapsed : " << (long double)(time_p) / CLOCKS_PER_SEC << endl;
}
signed main() {
  long long int testcase = 1;
  while (testcase--) {
    long long int n, i, x;
    cin >> n;
    if (n % 2 != 0)
      cout << -1;
    else {
      for (i = 1; i < n; i += 2) {
        cout << i + 1 << " " << i << " ";
      }
    }
    cout << "\n";
  }
  return 0;
}