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;
template <typename T>
void sorted(vector<T>& x, bool reverse = false) {
  if (reverse)
    sort(x.begin(), x.end(), greater<T>());
  else
    sort(x.begin(), x.end());
}
template <typename T>
void print(const vector<T>& x, const string sep = " ") {
  for (const T& temp : x) {
    cout << temp << sep;
  }
  cout << endl;
}
template <typename T>
T sum(const vector<T>& x) {
  return accumulate(x.begin(), x.end(), 0);
}
bool issquare(int64_t a) {
  return a == ((int64_t)(sqrt(a))) * ((int64_t)(sqrt(a)));
}
int64_t Digits(int64_t x) {
  int64_t result = 0;
  while (x != 0) {
    if (x % 10 == 4 or x % 10 == 7) {
      result++;
    }
    x /= 10;
  }
  return result;
}
void solve() {
  int64_t n;
  cin >> n;
  if (n % 2 == 0) {
    for (int64_t i = 0; i < n / 2; i++) {
      cout << 2 * i + 2 << " " << 2 * i + 1 << " ";
    }
    cout << endl;
  } else {
    cout << -1 << endl;
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  int testcases = 1;
  while (testcases--) solve();
}