#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  if (n == 6) {
    cout << 1 << " " << 2 << endl;
    cout << 1 << " " << 5 << endl;
    cout << 1 << " " << 6 << endl;
    cout << 2 << " " << 3 << endl;
    cout << 2 << " " << 4 << endl;
  } else if (n == 7) {
    cout << 1 << " " << 2 << endl;
    cout << 1 << " " << 6 << endl;
    cout << 1 << " " << 7 << endl;
    cout << 2 << " " << 3 << endl;
    cout << 2 << " " << 4 << endl;
    cout << 2 << " " << 5 << endl;
  } else if (n < 8)
    cout << -1 << endl;
  else {
    cout << 1 << " " << 2 << endl;
    cout << 1 << " " << 3 << endl;
    cout << 2 << " " << 4 << endl;
    cout << 4 << " " << 5 << endl;
    cout << 4 << " " << 6 << endl;
    cout << 3 << " " << 7 << endl;
    for (int i = 8; i <= n; i++) cout << 3 << " " << i << endl;
  }
  for (int i = 1; i < n; i++) {
    cout << i << " " << i + 1 << endl;
  }
  return 0;
}
