#include <bits/stdc++.h>
using namespace std;
int main() {
  int input;
  vector<int> ret;
  cin >> input;
  for (int i = 1; i < input; i += 2) {
    ret.push_back(i + 1);
    ret.push_back(i);
  }
  if (ret.empty() || ret.size() != input) ret = {-1};
  for (auto &d : ret) {
    cout << d << " ";
  }
  cout << endl;
  return 0;
}
