#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
const int INF = 0x7f7f7f7f;
int main() {
  int n;
  scanf("%d", &n);
  if (n < 6) {
    printf("-1\n");
    for (int i = 2; i <= n; i++) printf("%d %d\n", i - 1, i);
  } else {
    printf("1 2\n");
    printf("2 3\n");
    printf("3 4\n");
    for (int i = 5; i <= n; i++) {
      if (i & 1)
        printf("2 %d\n", i);
      else
        printf("3 %d\n", i);
    }
    for (int i = 2; i <= n; i++) printf("%d %d\n", i - 1, i);
  }
  return 0;
}
