#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  if (n < 6)
    cout << "-1\n";
  else if (n == 6) {
    cout << "1 2\n";
    cout << "1 3\n";
    cout << "1 4\n";
    cout << "3 5\n";
    cout << "3 6\n";
  } else if (n == 7) {
    cout << "1 2\n";
    cout << "1 3\n";
    cout << "1 4\n";
    cout << "3 5\n";
    cout << "3 6\n";
    cout << "3 7\n";
  } else {
    cout << "1 2\n";
    cout << "1 3\n";
    cout << "3 6\n";
    cout << "2 4\n";
    cout << "2 5\n";
    cout << "4 8\n";
    cout << "4 7\n";
    for (int i = 9; i <= n; i++) cout << "3 " << i << endl;
  }
  for (int i = 1; i < n; i++) cout << i << " " << i + 1 << endl;
  return 0;
}
