#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9 + 7;
signed main() {
  std::ios::sync_with_stdio(0);
  std::cin.tie(0);
  ;
  int n;
  cin >> n;
  if (n <= 5) {
    cout << -1 << endl;
  } else {
    cout << "1 2" << endl;
    int l = (n - 2) / 2;
    for (int i = 3; i < 3 + l; i++) cout << 1 << " " << i << endl;
    for (int i = 3 + l; i <= n; i++) cout << 2 << " " << i << endl;
  }
  for (int i = 1; i < n; i++) cout << i << " " << i + 1 << endl;
}
