docs: public static void main(String[] args) throws IOException {
  		FileInputStream in = new FileInputStream("ctb_v6/processed/postagged.train");
  		FileOutputStream out = new FileOutputStream("ctb_v6/processed/nountagged.train");
  		Scanner scanner = new Scanner(in);
  		PrintWriter pw = new PrintWriter(out);
  		while(scanner.hasNext()) {
  			String line = scanner.nextLine();
  			if(line.trim().equals("")) {
  				pw.println();
  				continue;
  			}
  			
  			String[] sa = line.split("\t");
  			//System.out.println(sa[0] + " " + sa[1]);
  			if(sa[1].indexOf("-N") != -1) {
  				if(sa[1].indexOf("B-N") != -1)
  					pw.println(sa[0] + "\t" + "B");
  				else if(sa[1].indexOf("S-N") != -1)
  					pw.println(sa[0] + "\t" + "S");
  				else if(sa[1].indexOf("M-N") != -1)
  					pw.println(sa[0] + "\t" + "M");
  				else if(sa[1].indexOf("E-N") != -1)
  					pw.println(sa[0] + "\t" + "E");
  				else {
  					System.out.println("error!");
  					System.exit(1);
  				}
  			}
  			else
  				pw.println(sa[0] + "\t" + "O");
  		}
  		
  		scanner.close();
  		in.close();
  		pw.close();
  		out.close();
  	}