#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(n), bs(n);
  for (int64_t i = 0; i < n; i++) {
    cin >> as[i] >> bs[i];
  }

  int64_t c = 500000000000000000LL;

  vector<int64_t> us, vs;
  for (int64_t t = 0; t < 50; t++) {
    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)) {
          int64_t x = (as[i] + as[j]) / 2;
          int64_t y = (bs[i] + bs[j]) / 2;

          as[i] = as[j] = x;
          bs[i] = bs[j] = y;

          us.push_back(i + 1);
          vs.push_back(j + 1);

          goto next;
        }
      }
    }
  next:;
  }

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

  return 0;
}