main.cpp

#include <iostream>
#include <string>
#include <utility>
#include <vector>

using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, days_total;
    if (!(cin >> n >> days_total)) {
        return 0;
    }
    vector<int> diff(days_total + 3, 0);
    for (int i = 0; i < n; ++i) {
        int left, right;
        cin >> left >> right;
        ++diff[left];
        --diff[right + 1];
    }
    int active = 0;
    int max_open = -1;
    int first_peak = 0;
    vector<pair<int, int>> merged;
    int start = -1;
    for (int day = 1; day <= days_total; ++day) {
        active += diff[day];
        if (active > max_open) {
            max_open = active;
            first_peak = day;
        }
        if (active > 0 && start == -1) {
            start = day;
        }
        if (active == 0 && start != -1) {
            merged.push_back({start, day - 1});
            start = -1;
        }
    }
    if (start != -1) {
        merged.push_back({start, days_total});
    }
    cout << "max_open=" << max_open << "\n";
    cout << "first_peak_day=" << first_peak << "\n";
    cout << "merged=";
    if (merged.empty()) {
        cout << "NONE";
    } else {
        for (size_t i = 0; i < merged.size(); ++i) {
            if (i) {
                cout << '|';
            }
            cout << merged[i].first << '-' << merged[i].second;
        }
    }
    cout << "\n";
    return 0;
}