Task.txt

import java.io.*;

public class Task {
    public static void main(String[] args)throws IOException{
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String name1 = reader.readLine();
        String name2 = reader.readLine();
        String name3 = reader.readLine();
        FileOutputStream file1 = new FileOutputStream(name1);
        FileInputStream file2 = new FileInputStream(name2);
        FileInputStream file3 = new FileInputStream(name3);
        byte[] f2 = new byte[file2.available()];
        byte[] f3 = new byte[file3.available()];
        while (file2.available() > 0){
            int data = file2.read(f2);
            file1.write(f2);
        }
        while (file3.available() > 0){
            int data = file3.read(f3);
            file1.write(f3, file2.available(), data);
        }

        reader.close();
        file1.close();
        file2.close();
        file3.close();
    }
}