#include <bits/stdc++.h>
using namespace std;
void work(int n) {
  cout << "1 3" << endl;
  cout << "1 2" << endl;
  cout << "2 4" << endl;
  cout << "2 5" << endl;
  cout << "1 6" << endl;
  for (int k = 7; k <= n; k++) {
    if (k % 2)
      cout << "2 " << k << endl;
    else
      cout << "1 " << k << endl;
  }
}
int main() {
  int n;
  cin >> n;
  if (n <= 5) {
    cout << "-1" << endl;
  } else {
    work(n);
  }
  for (int i = 2; i <= n; i++) {
    cout << "1 " << i << endl;
  }
  return 0;
}
