#include <iostream>
#include <algorithm>
#include <vector>
#include <cassert>
#include <climits>
#include <cstdio>

using namespace std;

#define MAX_N 10000

int N;

class Interval {
public:
  int left, right;
  Interval(int l = 0, int r = 0) : right(r), left(l) {}
};

ostream& operator <<(ostream& os, const Interval& interval) {
  return os << interval.left << " " << interval.right;
}

istream& operator >>(istream& is, Interval& interval) {
  return is >> interval.left >> interval.right;
}

Interval intervals[MAX_N];

vector<Interval*> dominating_set;

int main()
{
#ifdef EVAL
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif

  cin >> N;

  for (int i = 0; i < N; ++i) {
    cin >> intervals[i];
  }

  int upto = -1;
  for (;;) {
    int leftmost_right = INT_MAX;
    for (Interval* iter = intervals; iter != intervals+N; ++iter) {
      if ( iter->left > upto ) 
	if (iter->right < leftmost_right) 
	  leftmost_right = iter->right;
    }

     if (leftmost_right == INT_MAX) break;
    
    int rightmost_right = -1;
    Interval* max_interval;
    for (Interval* iter = intervals; iter != intervals+N; ++iter) {
      if ( iter->left > upto && iter->left <= leftmost_right) 
	if ( iter->right > rightmost_right ) {
	  rightmost_right = iter->right;
	  max_interval = iter;
	}
    }    
    dominating_set.push_back(max_interval);
    upto = rightmost_right;
  }

  cout << dominating_set.size() << endl;
  for (vector<Interval*>::iterator iter = dominating_set.begin(); iter != dominating_set.end(); ++iter) 
    cout << (*iter)->left << " " << (*iter)->right << endl;
}