#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  if (n < 6)
    cout << -1 << "\n";
  else {
    cout << "1 2\n";
    cout << "2 3\n";
    cout << "2 4\n";
    cout << "3 5\n";
    cout << "3 6\n";
    for (int i = 7; i <= n; i++) cout << 3 << " " << i << "\n";
  }
  for (int i = 2; i <= n; i++) cout << i - 1 << " " << i << "\n";
  return 0;
}
