org 256

	mov ah,0fh
	int 10h
	cbw
	push ax
	mov al,13h
	int 10h

        std
	cwd
	xor bx,bx
	mov cx,0ffffh
	mov si,diff+11
	mov es,[si]
step	add dh,[si]
	add cx,[si-2]
part	mov ax,1010h
	int 10h
	inc bx
	test bl,03fh
	jnz step
	lodsb
	lodsw
	and bh,bh
	jz part

	xor cx,cx
line	xor ah,ah
	xchg ax,bx
	mov di,199*320
	mov ax,255
	sub ax,bx
	test al,1
	jnz even
	mov di,256
	mov al,64
	mov cl,199
	add ax,bx	
even	cwd
	xchg ax,bp
	mov ax,di
	mov si,320
	div si
	sub cx,ax
	jnc yfix
	neg cx
	neg si
yfix	mov al,1
	xchg ax,bp
	sub ax,dx
	jnc xfix
	neg bp
	neg ax
xfix	cmp ax,cx
	jc lfix
	xchg ax,cx
	xchg si,bp
lfix	mov bh,al
	mov dx,cx
	neg dx
	sar dx,1
	mov ax,cx
	xchg ax,bx
	inc cx
plot	stosb
	inc di
	add di,si
	add dl,ah
	adc dh,0
	jnc skip
	add di,bp
	sub dx,bx
skip	loop plot
	inc al
	jnz line	

	mov ah,8
	int 21h
	pop ax
	int 10h
	ret

diff    db 0,0,1,1,1,-1,-1,-1,1,1,0,0,0a0h