#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  if (n == 1)
    cout << -1;
  else if (n % 2 == 0) {
    for (int i = n; i > 0; i--) cout << i << " ";
  } else if (n % 2 != 0)
    cout << -1;
}
