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