#include <bits/stdc++.h>
using namespace std;
long long power(long long a, long long p) {
  long long ret = 1;
  while (p > 0) {
    if (p & 1) {
      ret *= a;
    }
    a *= a;
    p >>= 1;
  }
  return ret;
}
long long powmod(long long a, long long b, long long MOD) {
  if (b == 0) return 1;
  long long x = powmod(a, b / 2, MOD);
  long long y = (x * x) % MOD;
  if (b % 2) return (a * y) % MOD;
  return y % MOD;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long n, i, j, x, y, k, m;
  string s;
  cin >> n;
  if (n <= 5)
    cout << "-1" << endl;
  else {
    if (n % 2) {
      x = (n - 1) / 2;
      for (i = 2; i <= x + 1; i++) cout << "1 " << i << endl;
      for (i = x + 2; i <= n; i++) cout << "2 " << i << endl;
    } else {
      x = (n - 1) / 2;
      for (i = 2; i <= x + 2; i++) cout << "1 " << i << endl;
      for (i = x + 3; i <= n; i++) cout << "2 " << i << endl;
    }
  }
  for (i = 1; i < n; i++) cout << i << " " << i + 1 << endl;
  return 0;
}
