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