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