#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int n;
  cin >> n;
  if (n < 6) {
    cout << -1 << " "
         << "\n";
    for (long long int i = 2; i <= n; ++i) {
      cout << 1 << " " << i << "\n";
    }
  } else {
    for (long long int i = 2; i <= n - 2; ++i) {
      cout << 1 << " " << i << "\n";
    }
    cout << 2 << " " << n - 1 << "\n";
    cout << 2 << " " << n << "\n";
    for (long long int i = 2; i <= n; ++i) {
      cout << 1 << " " << i << "\n";
    }
  }
}
