#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  if (n <= 5) {
    printf("-1\n");
  } else {
    for (int i = 2; i <= n; i += 2) printf("%d %d\n", 1, i);
    for (int i = 3; i <= n; i += 2) printf("%d %d\n", 2, i);
  }
  for (int i = 1; i < n; ++i) printf("%d %d\n", i, i + 1);
  return 0;
}
