一直runtime，StringTokenizer和Scanner都试过了，还是不行
用这个替换之后，AC了
static class sc{
        static BufferedReader reader;
        static StringTokenizer tokenizer;
        static void init(InputStream input){
            reader=new BufferedReader(new InputStreamReader(input));
            tokenizer=new StringTokenizer("");
        }
        static String next() throws IOException{
            while(!tokenizer.hasMoreTokens()){
                tokenizer=new StringTokenizer(reader.readLine());
            }
            return tokenizer.nextToken();
        }
        static int nextInt() throws IOException{
            return Integer.parseInt(next());
        }

    }