摘要：
C. Sorting Railway CarsAn infinitely long railway has a train consisting ofncars, numbered from1ton(the numbers of all the cars are distinct) and posi... 阅读全文
摘要：
A. Magic SpheresCarl is a beginner magician. He hasablue,bviolet andcorange magic spheres. In one move he can transform two spheresof the same colorin... 阅读全文