#include <iostream>
#include <thread>
#include <chrono>
using namespace std;
class Timer {
public:
    int hours, minutes, seconds;
    Timer(int h, int m, int s) : hours(h), minutes(m), seconds(s) {}
    void display() const {
        cout << (hours < 10 ? "0" : "") << hours << ":"
             << (minutes < 10 ? "0" : "") << minutes << ":"
             << (seconds < 10 ? "0" : "") << seconds << endl;
    }
    void tick() {
        if (seconds > 0) {
            --seconds;
        } else {
            if (minutes > 0) {
                --minutes;
                seconds = 59;
            } else if (hours > 0) {
                --hours;
                minutes = 59;
                seconds = 59;
            }
        }
    }

    bool finished() const {
        return hours == 0 && minutes == 0 && seconds == 0;
    }
    void start() {
        while (!finished()) {
            display();
            this_thread::sleep_for(chrono::seconds(1));
            tick();
        }
        cout << "Time's up!" << endl;
    }
};

int main() {
    Timer timer(0, 0, 10);  
    cout << "Starting countdown timer:\n";
    timer.start();
    return 0;
}