The code seems working but fails to pass verification

package com.codegym.task.task18.task1825; import java.io.*; import java.util.*; /* Building a file */ public class Solution { public static void main(String[] args) throws IOException { String prefix="C:\\Users\\k.shayakhmetov\\Desktop\\CodeGym\\CodeGymTasks\\CodeGymTasks\\2.JavaCore\\src\\com\\codegym\\task\\task18\\task1825\\"; //read file names from the console //read in file names Scanner scanner=new Scanner(System.in); ArrayList<String> fileNames=new ArrayList<>(); String temp; while (!(temp=scanner.nextLine()).equals("")){ if (temp.equals("end")) { scanner.close(); break; } else { fileNames.add(temp); System.out.println(temp); } } //extract the fileName without part# String tempFileName=fileNames.get(0); int index=tempFileName.indexOf("part"); String fileToWrite=tempFileName.substring(0,index-1); TreeMap<Integer, String> map=new TreeMap<>(); for (String fileName : fileNames) { String[] split = fileName.split("\\."); int key = Integer.parseInt(String.valueOf(split[2].charAt(split[2].length() - 1))); map.put(key, fileName); } FileOutputStream fileOutputStream=new FileOutputStream(new File(prefix+fileToWrite), true); BufferedOutputStream bos=new BufferedOutputStream(fileOutputStream, 1000); readFile(map, bos); bos.close();fileOutputStream.close(); } public static void readFile(TreeMap<Integer, String> map, BufferedOutputStream bos) throws IOException { String prefix="C:\\Users\\k.shayakhmetov\\Desktop\\CodeGym\\CodeGymTasks\\CodeGymTasks\\2.JavaCore\\src\\com\\codegym\\task\\task18\\task1825\\"; for (Map.Entry<Integer, String> pair:map.entrySet()){ FileInputStream fileInputStream=new FileInputStream(prefix+pair.getValue()); BufferedInputStream reader=new BufferedInputStream(fileInputStream, 1000); byte[] buffer = new byte[reader.available()]; byte read; while ((read = (byte)reader.read(buffer, 0, buffer.length)) > 0) { bos.write(buffer, 0, read); } reader.close(); fileInputStream.close(); } } }