#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  int n;
  cin >> n;
  if (n <= 5) {
    cout << -1 << "\n";
  } else if (n == 6) {
    cout << 1 << " " << 2 << "\n"
         << 2 << " " << 3 << "\n"
         << 2 << " " << 4 << "\n"
         << 3 << " " << 5 << "\n"
         << 3 << " " << 6 << "\n";
  } else {
    int i;
    for (i = 2; i <= n - 3; i++) {
      cout << 1 << " " << i << "\n";
    }
    for (; i <= n; i++) {
      cout << 2 << " " << i << "\n";
    }
  }
  for (int i = 2; i <= n; i++) {
    cout << 1 << " " << i << "\n";
  }
  return 0;
}
