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