#include <bits/stdc++.h>
using namespace std;
using namespace chrono;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;
#endif

int main() {
  int64_t n;
  cin >> n;
  vector<int64_t> as_64(n), bs_64(n);
  for (int64_t i = 0; i < n; i++) {
    cin >> as_64[i] >> bs_64[i];
  }

  vector<__int128_t> as(n), bs(n);
  for (int64_t i = 0; i < n; i++) {
    as[i] = as_64[i];
    bs[i] = bs_64[i];
  }

  __int128_t c = 500000000000000000LL;

  vector<int64_t> us, vs;
  for (int64_t t = 0; t < 50; t++) {
    int64_t u = -1, v = -1;

    for (int64_t i = 0; i < n; i++) {
      for (int64_t j = i + 1; j < n; j++) {
        if ((as[i] < c) != (as[j] < c) && (bs[i] < c) != (bs[j] < c)) {
          if (u == -1 ||
              ((as[i] - c) + (as[j] - c)) * ((as[i] - c) + (as[j] - c)) +
                      ((bs[i] - c) + (bs[j] - c)) *
                          ((bs[i] - c) + (bs[j] - c)) <
                  ((as[u] - c) + (as[v] - c)) * ((as[u] - c) + (as[v] - c)) +
                      ((bs[u] - c) + (bs[v] - c)) *
                          ((bs[u] - c) + (bs[v] - c))) {
            u = i;
            v = j;
          }
        }
      }
    }

    if (u != -1) {
      int64_t x = (as[u] + as[v]) / 2;
      int64_t y = (bs[u] + bs[v]) / 2;

      as[u] = as[v] = x;
      bs[u] = bs[v] = y;

      us.push_back(u + 1);
      vs.push_back(v + 1);
    }
  }

  cout << us.size() << endl;
  for (int64_t i = 0; i < us.size(); i++) {
    cout << us[i] << ' ' << vs[i] << endl;
  }

  return 0;
}