#include <bits/stdc++.h>
using namespace std;
vector<long long> v1;
vector<long long>::iterator upper, lower, it;
vector<vector<long long>> adj(200005);
unordered_map<long long, long long> mp;
void correctalgo(long long n) {
  long long i;
  for (i = 1; i < n; i++) {
    cout << i << " " << i + 1 << "\n";
  }
}
void wrongalgo(long long n) {
  long long i;
  cout << 1 << " " << 2 << "\n";
  for (i = 3; i < 3 + (n - 2) / 2; i++) {
    cout << 2 << " " << i << "\n";
  }
  for (i = 3 + (n - 2) / 2; i <= n; i++) {
    cout << 1 << " " << i << "\n";
  }
}
void solve() {
  long long n = 0, m = 0, i = 0, j = 0, l = 0, r = 0, x = 0, y = 0, q = 0,
            z = 0, len = 0, k = 0, p = 0;
  long long a[200005] = {0}, b[200005] = {0}, c[200005] = {0}, d[200005] = {0};
  char s[300005], t[300005];
  cin >> n;
  if (n < 6) {
    cout << "-1"
         << "\n";
    correctalgo(n);
    return;
  }
  wrongalgo(n);
  correctalgo(n);
}
bool imp = false;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t = 1;
  if (imp) cin >> t;
  while (t--) solve();
  return 0;
}
