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