#include <bits/stdc++.h>
using namespace std;
int const N = 1e5 + 5;
int const MAX = 1e9 + 5;
int n;
void incorrect() {
  if (n <= 5) {
    cout << -1 << endl;
    return;
  }
  cout << 1 << " " << 2 << endl;
  for (int i = 3; i <= n; i++) {
    if (i % 2 == 1) {
      cout << 1 << " " << i << endl;
    } else {
      cout << 2 << " " << i << endl;
    }
  }
}
void correct() {
  for (int i = 2; i <= n; i++) cout << i - 1 << " " << i << endl;
}
int main() {
  cin >> n;
  incorrect();
  correct();
}
