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#if defined(EMBE_DEBUG) && !defined(NDEBUG)
#include "embe-debug.hpp"
#else
#define LOG_INDENT(...) do {} while (false)
#define LOG(...) do {} while (false)
#define DUMP(...) do {} while (false)
#endif

#include <iostream>
#include <vector>
using namespace std;

namespace {

vector<vector<int>> make(int k)
{
  vector<vector<int>> res;

  auto new_node = [&]() {
    res.emplace_back();
    return int(res.size() - 1);
  };

  auto add = [&](int a, int b) {
    res[a].emplace_back(b);
  };

  constexpr int LAST = -1;

  int c = new_node();
  int p = LAST;

  while (true) {
    if (k % 2 == 1) {
      add(c, p);
      if (k > 1) {
        int d = new_node();
        add(c, d);
        c = d;
      }
    }
    k /= 2;
    if (k == 0) break;
    int q = new_node();
    int r = new_node();
    add(q, r);
    add(q, p);
    add(r, p);
    p = q;
  }

  int last = new_node();
  for (auto& v: res) {
    for (auto& w: v) {
      if (w == LAST) w = last;
    }
  }
  return res;
}

}

int main()
{
  iostream::sync_with_stdio(false);
  cin.tie(nullptr);

  int k;
  cin >> k;

  auto res = make(k);
  cout << res.size() << endl;
  for (auto const& v: res) {
    int q = v.size();
    cout << (q > 0 ? v[0] + 1 : -1);
    cout << ' ';
    cout << (q > 1 ? v[1] + 1 : -1);
    cout << '\n';
  }

  return 0;
}