#include <iostream>
#include <algorithm>
#include <string>
#include <vector>

using namespace std;

vector < int > answer;

int f(int x, vector < int > v)
{
    int max = -INT_MIN, max_i;
    if (x < int(v.size()) - 1)
    {
        for (int i = x + 1; i < int(v.size()); i++)
            if (v[i] > max)
                max = v[i] + 1;
    }
    else
        max = 0;
    return max;
}

void w(int x, vector <int > v, vector < int > c)
{
    int max = -1, max_i;
    for (int i = x + 1; i < int(v.size()); i++)
        if (c[i] >= max)
        {
            max = c[i];
            max_i = i;
        }
    answer.push_back(max_i);
    if (c[max_i] > 0)
        w(v[max_i], v, c);
}
int main()
{
    int n, x, y;
    vector < pair < int, int > > a;
    vector < pair < int, int > > coordinate;
    vector < int > b;
    cin >> n;
    for (int i = 0; i < n; i++)
    {
        cin >> x >> y;
        a.push_back(make_pair(x, y));
    }
    sort(a.begin(), a.end());
    for (int i = 0; i < n; i++)
    {
        coordinate.push_back(make_pair(a[i].first, i));
        coordinate.push_back(make_pair(a[i].second, i));
    }
    sort(coordinate.begin(), coordinate.end());
    int open = 0;
    for (int i = 0; i < n * 2; i++)
    {
        if (int(b.size()) <= coordinate[i].second)
        {
            b.push_back(-1);
            open = coordinate[i].second;
        }
        else
            b[coordinate[i].second] = open;
    }
    vector < int > c = b;
    for (int i = int(b.size()) - 1; i >= 0; i--)
            c[i] = f(b[i], c);
    c[0] += 1;
    int max = -1, max_i;
    for (int i = 0; i < n; i++)
        if (c[i] > max)
        {
            max = c[i];
            max_i = i;
        }
    answer.push_back(max_i);
    w(b[max_i], b, c);
    cout << answer.size() << endl;
    for (int i = 0; i < int(answer.size()); i++)
        cout << a[answer[i]].first << ' '<< a[answer[i]].second << endl;
}