rt，这道题对java选手需要使用优化的快读快写来进行读入输出，否则就算代码正确也会mle几个点的

快读快写

static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    static StreamTokenizer st = new StreamTokenizer(br);
    static PrintWriter pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));