32 typedef std::chrono::milliseconds ms;  typedef
39     std::this_thread::sleep_for(ms(200));  in f0()
48     std::this_thread::sleep_for(ms(200));  in f1()
55     std::this_thread::sleep_for(ms(200));  in f2()
61     std::this_thread::sleep_for(ms(200));  in f3()
68     std::this_thread::sleep_for(ms(200));  in f4()
74     std::this_thread::sleep_for(ms(200));  in f5()
86     std::this_thread::sleep_for(ms(300));  in test()
100         assert(t1-t0 > ms(100));  in test()
102         assert(t1-t0 < ms(100));  in test()
146         std::this_thread::sleep_for(ms(300));  in main()
151         std::this_thread::sleep_for(ms(300));  in main()