main.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <map>

using namespace std;

struct Record
{
    int id;
    int loc;
    int delta;
};

int main()
{
    int n;
    cin >> n;

    vector<Record> v;

    for (int i = 0; i < n; i++)
    {
        int from, to;
        cin >> from >> to;

        v.push_back({i, from, 1});
        v.push_back({i, to, -1});
    }

    sort(v.begin(), v.end(), [](const Record &a, const Record &b) {
        return a.loc > b.loc;
    });
    reverse(v.begin(), v.end());

    vector<int> ans;
    
    while (!v.empty())
    {
        int max_points = 0, current_points = 0, biggest_loc = 0;

        for (int i = 0; i < v.size(); i++)
        {
            current_points += v[i].delta;
            if (current_points >= max_points)
            {
                biggest_loc = v[i].loc;
                max_points = current_points;
            }
        }

        map<int, int> met;


        for (int i = 0; i < v.size() && v[i].loc <= biggest_loc; i++)
        {
            met[v[i].id] += v[i].delta;
        }

        ans.push_back(biggest_loc);

        v.erase(remove_if(v.begin(), v.end(), [&](const Record &obj) { return met[obj.id] > 0; }), v.end());
    }

    cout << ans.size() << "\n";

    for (auto o : ans)
    {
        cout << o << " ";
    }
}