#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n;
  cin >> n;
  if (n <= 5) {
    cout << -1 << endl;
    for (int i = 2; i <= n; i++) {
      cout << 1 << " " << i << endl;
    }
  } else {
    if (n % 2 == 0) {
      int k = (n / 2);
      int j = 2;
      while (k--) {
        cout << 1 << " " << j << endl;
        j++;
      }
      k = (n / 2) - 1;
      while (k--) {
        cout << 2 << " " << j << endl;
        j++;
      }
    } else {
      int k = n - 1;
      k = k / 2;
      int j = 2;
      while (k--) {
        cout << 1 << " " << j << endl;
        j++;
      }
      k = (n - 1) / 2;
      while (k--) {
        cout << 2 << " " << j << endl;
        j++;
      }
    }
    for (int i = 2; i <= n; i++) {
      cout << 1 << " " << i << endl;
    }
  }
  return 0;
}
