#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  if (n < 6) {
    cout << -1 << "\n";
  } else {
    for (int i = 0; i < n - 6; i++) {
      cout << i + 1 << " " << i + 2 << "\n";
    }
    cout << n - 5 << " " << n - 4 << "\n";
    cout << n - 5 << " " << n - 3 << "\n";
    cout << n - 5 << " " << n - 2 << "\n";
    cout << n - 2 << " " << n - 1 << "\n";
    cout << n - 2 << " " << n << "\n";
  }
  for (int i = 0; i < n - 1; i++) {
    cout << i + 1 << " " << i + 2 << "\n";
  }
}
