#include <thread>                                                                                                       
#include <mutex>                                                                                                        
#include <atomic>                                                                                                       
                                                                                                                        
int main()                                                                                                              
{                                                                                                                       
    std::atomic<bool> stop = false;                                                                                     
    std::mutex m1, m2, m3;                                                                                              
                                                                                                                        
    std::thread a([&] {                                                                                                 
        while (!stop) {                                                                                                 
            std::lock_guard l1(m1);                                                                                     
            std::lock_guard l2(m2);                                                                                     
        }                                                                                                               
    });                                                                                                                 
                                                                                                                        
    std::thread b([&] {                                                                                                 
        while (!stop) {                                                                                                 
            {                                                                                                           
                std::lock_guard l2(m2);                                                                                 
                std::lock_guard l3(m3);                                                                                 
            }                                                                                                           
            {                                                                                                           
                std::lock_guard l3(m3);                                                                                 
                std::lock_guard l1(m1);                                                                                 
            }                                                                                                           
        }                                                                                                               
    });                                                                                                                 
                                                                                                                           
    using namespace std::chrono_literals;                                                                                  
    std::this_thread::sleep_for(3s);                                                                                       
                                                                                                                                                                                                                   
    stop = true;                                                                                                           
    a.join();                                                                                                           
    b.join();                                                                                                           
}