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

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

#define rep(i,n) for(int i = 0; i < (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define rng(a) a.begin(),a.end()
#define rrng(a) a.rbegin(),a.rend()
template<typename T> using vc = vector<T>;
template<typename T> using vv = vc<vc<T>>;
template<typename T> using PQ = priority_queue<T,vc<T>,greater<T> >;
template<typename T>void uni(T& a){sort(rng(a));a.erase(unique(rng(a)),a.end());}
using ll = long long;
using P = pair<int,int>;
int dx[4] = {-1,0,1,0};
int dy[4] = {0,-1,0,1};
constexpr int INF = 1001001001;
constexpr ll INFL = 1001002003004005006ll;


inline unsigned long long xor128() {
	static unsigned long long rx = 123456789, ry = 986960440, rz = 738905609, rw = 23140692;
	unsigned long long rt = (rx ^ (rx << 11));
	rx = ry;ry = rz;rz = rw;
	return (rw = (rw ^ (rw >> 19)) ^ (rt ^ (rt >> 8)));
}
inline float rand128(float min = 0, float max = 1){
	return (float)(xor128() % 0xFFFF) / 0xFFFF * (max - min) + min;
}
inline unsigned long long randint(int min, int max){
	return xor128()%(max - min + 1) + min;
}

class TimeKeeper {
private:
  std::chrono::high_resolution_clock::time_point start_time_;
  int64_t time_threshold_;
public:
  TimeKeeper(const int64_t& time_threshold)
    : start_time_(std::chrono::high_resolution_clock::now()),
      time_threshold_(time_threshold) 
      {}
  bool isTimeOver() const {
    using std::chrono::duration_cast;
    using std::chrono::milliseconds;
    auto diff = std::chrono::high_resolution_clock::now() - this->start_time_;
    return duration_cast<milliseconds>(diff).count() >= time_threshold_;
  }
};

int used[55][55];

// グローバル変数
int n; // 頂点数
vector<ll> ga;
vector<ll> gb;
void read_input() {
  cin >> n;
  ga.resize(n);
  gb.resize(n);
  rep(i,n) cin >> ga[i] >> gb[i];
}

struct Output {
  int u,v;
  Output (int u=0, int v=0) : u(u), v(v) {}
};

struct State {
  vector<ll> a;
  vector<ll> b;  
  vector<Output> ans;

  State() {
    a.resize(n);
    b.resize(n);
    a = ga;
    b = gb;
  }
  
  void init() {
  }

  void make_init_ans() {
    rep(i,50) {
      int idx1 = randint(0,n-2);
      int idx2 = randint(0,n-1);
      if (idx1 == idx2) idx1++;
      ans.push_back(Output(idx1,idx2));
      ll va = (a[idx1]+a[idx2])/2;
      ll vb = (b[idx1]+b[idx2])/2;
      a[idx1] = a[idx2] = va;
      b[idx1] = b[idx2] = vb;
    }
  }

  void print_ans() {
    cout << ans.size() << endl;
    for (Output o : ans) {
      cout << o.u << " " << o.v << endl;
    }
  }

  void gready() {
    rep(i,20) {
      int idx1 = randint(0,n-2);
      int idx2 = randint(0,n-1);
      if (idx1 == idx2) idx1++;
      ans.push_back(Output(idx1+1,idx2+1));
      ll va = (a[idx1]+a[idx2])/2;
      ll vb = (b[idx1]+b[idx2])/2;
      a[idx1] = a[idx2] = va;
      b[idx1] = b[idx2] = vb;
    }
    vector<P> p;
    rep(i,20) {
      ll v1 = abs(5e17-a[0]);
      ll v2 = abs(5e17-b[0]);
      ll best_score = INFL;
      int best_j = -1;
      int best_k = -1;
      for (int j=0; j<n; j++) {
        for (int k=j+1; k<n; k++) {
          ll va = (a[k]+a[j])/2;
          ll vb = (b[k]+b[j])/2;
          ll score = abs(va-vb);
          if (used[j][k]) continue;
          if (best_score > score) {
            best_score = score;
            best_j = j;
            best_k = k;
          }
        }
      }
      if (best_j == -1) continue;
      ans.push_back(Output(best_j+1,best_k+1));
      ll va = (a[best_k]+a[best_j])/2;
      ll vb = (b[best_k]+b[best_j])/2;
      a[best_k] = a[best_j] = va;
      b[best_k] = b[best_j] = vb;
      p.push_back(P(best_j,best_k));
      used[best_j][best_k] = 1;
    }
    for (auto v : p) used[v.first][v.second] = 0;
    rep(i,10) {
      ll v1 = abs(5e17-a[0]);
      ll v2 = abs(5e17-b[0]);
      ll best_score = INFL;
      int best_j = -1;
      for (int j=1; j<n; j++) {
        ll va = (a[0]+a[j])/2;
        ll vb = (b[0]+b[j])/2;
        ll vva = abs(5e17-va);
        ll vvb = abs(5e17-vb);
        ll score = max(vva,vvb);
        if (best_score > score) {
          best_score = score;
          best_j = j;
        }
      }
      if (best_j == -1) continue;
      ans.push_back(Output(1,best_j+1));
      ll va = (a[0]+a[best_j])/2;
      ll vb = (b[0]+b[best_j])/2;
      a[0] = a[best_j] = va;
      b[0] = b[best_j] = vb;
    }    
  }

  ll calc_score() {
    ll V1 = abs(a[0]-5e17);
    ll V2 = abs(b[0]-5e17);
    return 2000000 - 100000*log10(max(V1,V2)+1);
  }

};

void simulatedAnnealing() {
  TimeKeeper timer(950);
  State state;
  state.gready();
  state.calc_score();
  ll score = state.calc_score();
  ll best_score = score;
  auto best_state = state;
  int iter_count = 0;

  while (!timer.isTimeOver()) {
    iter_count++;
    State next_state;
    next_state.gready();
    next_state.calc_score();
    ll next_score = next_state.calc_score();    

    if (next_score > best_score) {
      best_score = next_score;
      best_state = next_state;
      // cerr << "best score: " << best_score << endl;
    }
  }
  best_state.print_ans();
  // cerr << "best_score:" << "\t" << best_score << endl;
  // cerr << "iter_count:" << "\t" << iter_count << endl;
}

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