#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>
#include <chrono>
using namespace std;

// #include <atcoder/all>
// using namespace atcoder;

#define rep(i, n) for (int i = 0; i < (n); ++i)
#define ll long long
static constexpr ll INF = 1e18;
static constexpr int inf = 1e9;

const double TIME_LIMIT = 990;
const long long VAL = 5e17;
const int OP_SIZE = 50;

const long long N = 45;
long long A[N];
long long B[N];

// Random
namespace titan23 {

  struct Random {
    unsigned int _x, _y, _z, _w;

    Random() {
      _x = 123456789;
      _y = 362436069;
      _z = 521288629;
      _w = 88675123;
    }

    unsigned int _xor128() {
      unsigned int t = _x ^ (_x << 11);
      _x = _y;
      _y = _z;
      _z = _w;
      _w = (_w ^ (_w >> 19)) ^ (t ^ (t >> 8));
      return _w;
    }

    double random() {
      return (double)(_xor128()) / 0xFFFFFFFF;
    }

    int randint(int begin, int end) {
      assert(begin <= end);
      return begin + _xor128() % (end - begin + 1);
    }

    double randdouble(double begin, double end) {
      assert(begin < end);
      return begin + random() * (end-begin);
    }

    int randrange(int begin, int end) {
      assert(begin < end);
      return begin + _xor128() % (end - begin);
    }

    template <typename T>
    void shuffle(vector<T> &a) {
      int n = (int)a.size();
      for (int i = 0; i < n-1; ++i) {
        int j = randrange(i, n);
        swap(a[i], a[j]);
      }
    }

    template <typename T>
    T choice(const vector<T> &a) {
      int i = randrange(0, a.size());
      return a[i];
    }

    template <typename T>
    T choice(const vector<T> &a, const vector<int> &w, bool normal) {
      assert(normal == false);
      assert(a.size() == w.size());
      double sum = 0.0;
      for (const int &x: w) sum += x;
      assert(sum > 0);
      vector<double> x(w.size());
      for (int i = 0; i < x.size(); ++i) {
        x[i] = (double)w[i] / sum;
        if (i-1 >= 0) x[i] += x[i-1];
      }
      return choice(a, x);
    }

    template <typename T>
    T choice(const vector<T> &a, const vector<double> &w) {
      double i = random();
      int l = -1, r = a.size()-1;
      while (r - l > 1) {
        int mid = (l + r) / 2;
        if (w[mid] <= i) l = mid;
        else r = mid;
      }
      return a[r];
    }
  };
} // namespace titan23

titan23::Random myrandom;

// Timer
namespace titan23 {
  class Timer {
  public:
    Timer() : start_timepoint(std::chrono::high_resolution_clock::now()) {}

    void reset() {
      start_timepoint = std::chrono::high_resolution_clock::now();
    }

    double elapsed() {
      auto end_timepoint = std::chrono::high_resolution_clock::now();
      auto start = std::chrono::time_point_cast<std::chrono::microseconds>(start_timepoint).time_since_epoch().count();
      auto end = std::chrono::time_point_cast<std::chrono::microseconds>(end_timepoint).time_since_epoch().count();
      return (end - start) * 0.001; // ミリ秒単位で経過時間を返す
    }

  private:
    std::chrono::time_point<std::chrono::high_resolution_clock> start_timepoint;
  };
}

// SA 最小化
namespace titan23 {

namespace sa {

  titan23::Random sa_random;

  using Changed = vector<pair<int, int>>;

  struct State {
    double score;
    vector<pair<int, int>> op;

    State() : score(0.0) {}

    double get_score() const {
      ll a[N], b[N];
      rep(i, N) {
        a[i] = A[i];
        b[i] = B[i];
      }
      for (auto &[u, v]: op) {
        ll x = (a[u]+a[v])/2;
        a[u] = x;
        a[v] = x;
        ll y = (b[u]+b[v])/2;
        b[u] = y;
        b[v] = y;
      }
      return max(abs(VAL-a[0]), abs(VAL-b[0])) / 1e4;
    }

    Changed modify() {
      vector<pair<int, int>> pre_op = op;
      double prob = myrandom.random();
      if (op.empty() || (prob < 0.1 && op.size()+1 <= OP_SIZE)) {
        int indx = myrandom.randint(0, op.size());
        int u = myrandom.randrange(0, N);
        int v = myrandom.randrange(0, N);
        while (u == v) {
          v = myrandom.randrange(0, N);
        }
        pair<int, int> uv = {u, v};
        op.insert(op.begin()+indx, uv);
      } else {
        assert(!op.empty());
        int indx = myrandom.randrange(0, op.size());
        op.erase(op.begin() + indx);
      }
      return pre_op;
    }

    void rollback(Changed &changed) {
      op = changed;
    }
  };

  // TIME_LIMIT: ms
  State run(const double TIME_LIMIT) {
    titan23::Timer sa_timer;

    double START_TEMP = 100.0;
    double END_TEMP = 1.0;
    double TEMP_VAL = (START_TEMP - END_TEMP) / TIME_LIMIT;

    auto make_ans_init = [&] () -> State {
      State state;
      return state;
    };

    State ans = make_ans_init();
    State best_ans = ans;
    double score = ans.get_score();
    double best_score = score;

    int cnt = 0;
    while (true) {
      double now_time = sa_timer.elapsed();
      if (now_time > TIME_LIMIT) break;
      ++cnt;
      Changed changed = ans.modify();
      double new_score = ans.get_score();
      double arg = score - new_score;
      if (arg >= 0 || exp(arg/(START_TEMP-TEMP_VAL*now_time)) > sa_random.random()) {
        score = new_score;
        if (score < best_score) {
          best_score = score;
          best_ans = ans;
        }
      } else {
        ans.rollback(changed);
      }
    }
    cerr << "cnt=" << cnt << endl;
    cerr << "score=" << best_score << endl;
    return best_ans;
  }
}
}  // namespace titan23

using namespace titan23;

void solve() {
  int n_;
	cin >> n_;
	rep(i, N) cin >> A[i] >> B[i];

  sa::State ans = sa::run(TIME_LIMIT);


	cout << ans.op.size() << endl;
  for (auto &[u, v]: ans.op) {
    cout << u+1 << ' ' << v+1 << endl;
  }
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  solve();
  return 0;
}