#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, temp1, temp2;
  cin >> n;
  if (n <= 5) {
    cout << "-1" << endl;
    for (int i = 2; i <= n; i++) cout << "1 " << i << endl;
    return 0;
  }
  cout << "1 2" << endl;
  cout << "2 3" << endl;
  cout << "2 4" << endl;
  for (int i = 5; i <= n; i++) cout << "1 " << i << endl;
  for (int i = 2; i <= n; i++) cout << "1 " << i << endl;
  return 0;
}
