#include <bits/stdc++.h>
using namespace std;
const int S = 12345;
int main() {
  int n;
  while (scanf("%d", &n) == 1) {
    if (n == 2) {
      printf("-1\n");
      printf("1 2\n");
    } else if (n == 3) {
      printf("-1\n");
      printf("1 2\n2 3\n");
    } else if (n == 4) {
      printf("-1\n");
      printf("1 2\n1 3\n1 4\n");
    } else if (n == 5) {
      printf("-1\n");
      printf("1 2\n1 3\n1 4\n1 5\n");
    } else {
      printf("1 2\n1 3\n1 4\n");
      for (int i = 5; i <= n; i++) printf("2 %d\n", i);
      printf("1 2\n");
      for (int i = 3; i <= n; i++) printf("2 %d\n", i);
    }
  }
  return 0;
}
