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