1E

#include <algorithm>
#include <cmath>
#include <iostream>
#include <vector>

using std::cin;
using std::cout;
using std::max;
using std::min;
using std::string;
using std::vector;
using Pii = std::pair<int, int>;

bool Cmp(Pii aa, Pii bb) {
  return aa.first < bb.first || (aa.first == bb.first && aa.second > bb.second);
}

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);
  std::cout.tie(0);
  int nn;
  cin >> nn;
  vector<Pii> aa;
  for (int ii = 0; ii < nn; ++ii) {
    int li;
    int ri;
    cin >> li >> ri;
    aa.push_back({li, 1});
    aa.push_back({ri, -1});
  }
  sort(aa.begin(), aa.end(), Cmp);
  /*cout << "SORTED\n";
  for (auto pp: aa) {
    cout << pp.first << ' ' << pp.second << "\n";
  }*/
  vector<Pii> ans;
  int bal = 0;
  int lbound;
  int rbound;
  for (int ii = 0; ii < nn * 2; ++ii) {
    bal += aa[ii].second;
    if (bal == 1 && aa[ii].second == 1) {
      lbound = aa[ii].first;
      // cout << "l r = " << lbound << ' ' << rbound << "\n";
    }
    if (bal == 0) {
      rbound = aa[ii].first;
      // cout << "l r = " << lbound << ' ' << rbound << "\n";
      ans.push_back({lbound, rbound});
    }
  }
  cout << ans.size() << "\n";
  for (auto pp : ans) {
    cout << pp.first << ' ' << pp.second << "\n";
  }
}