#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i;
  cin >> n;
  if (n < 6)
    cout << "-1" << endl;
  else {
    cout << "1 2\n2 3\n3 4\n3 5\n2 6" << endl;
    for (i = 7; i <= n; i++) cout << "2 " << i << endl;
  }
  for (i = 2; i <= n; i++) cout << "1 " << i << endl;
}
