In Codeforces Round # 439 (Div. 2), my B title was hacked so that I late passed through for 1 hour and lost a lot of points. The first hack, or a bit uncomfortable. But also told me that their code ability is still relatively weak, error correction capability has yet to be improved.Although hacker Dragon made me rank behind, but from a certain point of view, I would like to thank him. Because he made me discover my own shortcomings. (original is Chinese，Translation is provided by Google Translate)