#include <bits/stdc++.h>
using namespace std;
long long int pow_mod(long long int a, long long int b) {
  long long int res = 1;
  while (b != 0) {
    if (b & 1) {
      res = (res * a) % 1000000007;
    }
    a = (a * a) % 1000000007;
    b /= 2;
  }
  return res;
}
long long int k, n, a, b;
bool check(long long int val) {
  long long int z = k;
  z -= val * a;
  long long int ans = val;
  if (z <= 0) return false;
  long long int xx = 0;
  if (z > b) xx = (z - 1) / b;
  if (xx + val >= n) return true;
  return false;
}
bool is_prime(long long int n) {
  for (long long int i = 2; i * i <= n; i++)
    if (n % i == 0) return false;
  return true;
}
void solve() {
  long long int n;
  cin >> n;
  vector<pair<long long int, long long int> > a, b;
  for (long long int i = 1; i < n; i++) b.push_back(make_pair(i, i + 1));
  if (n > 5) {
    long long int i = 1;
    a.push_back(make_pair(1, 2));
    i++;
    i++;
    while (i <= (n + 2) / 2) {
      a.push_back(make_pair(i, 1));
      i++;
    }
    while (i <= n) {
      a.push_back(make_pair(i, 2));
      i++;
    }
  }
  if (a.empty())
    cout << "-1\n";
  else {
    for (long long int i = 0; i < a.size(); i++)
      cout << a[i].first << " " << a[i].second << endl;
  }
  for (long long int i = 0; i < b.size(); i++)
    cout << b[i].first << " " << b[i].second << endl;
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long int t;
  t = 1;
  while (t--) solve();
  return 0;
}
