#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int N;
  cin >> N;
  if (N < 6) {
    cout << -1 << endl;
  } else {
    cout << 1 << " " << 2 << endl;
    cout << 1 << " " << 3 << endl;
    cout << 1 << " " << 4 << endl;
    for (int i = 5; i <= N; ++i) printf("4 %d\n", i);
  }
  for (int i = 1; i <= N / 2; ++i) printf("1 %d\n", i + 1);
  int j = 2;
  for (int i = N / 2 + 1; i < N; ++i) printf("%d %d\n", j++, i + 1);
  return 0;
}
