#include <iostream>
 #include <thread>
 #include <chrono>
 #include <mutex>

 std::mutex display_mutex;

 void worker() {
     std::thread::id this_id = std::this_thread::get_id();

     display_mutex.lock();
     std::cout << "thread " << this_id << " sleeping...\n";
     display_mutex.unlock();

     std::this_thread::sleep_for(std::chrono::seconds(1));
 }

 int main() {
    std::thread t1(worker);
    std::thread::id t1_id = t1.get_id();

    std::thread t2(worker);
    std::thread::id t2_id = t2.get_id();

    display_mutex.lock();
    std::cout << "t1's id: " << t1_id << "\n";
    std::cout << "t2's id: " << t2_id << "\n";
    display_mutex.unlock();

    t1.join();
    t2.join();

    return 0;
 }