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