#include <bits/stdc++.h>
using namespace std;
const long long N = 200010;
inline long long read() {
  long long s = 0, w = 1;
  register char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') w = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9')
    s = (s << 3) + (s << 1) + (ch ^ 48), ch = getchar();
  return s * w;
}
long long n;
signed main() {
  n = read();
  if (n <= 5) {
    puts("-1");
    for (register long long i = 1; i < n; i++) printf("%lld %lld\n", i, i + 1);
    puts("");
    return 0;
  }
  for (register long long i = 2; i <= n / 2 + 1; i++) printf("1 %lld\n", i);
  for (register long long i = n / 2 + 2; i <= n; i++) printf("2 %lld\n", i);
  for (register long long i = 1; i < n; i++) printf("%lld %lld\n", i, i + 1);
  return 0;
}
