opt a+,o+,p+,o1+,o2+ 
 
 move.l 4(sp),a0
 move.w #1000-1,d0
 add.l #1000,a0
 
 tst:	tst.b -(a0)
 	bne.s stop
 	dbra d0,tst 
 	
 	clr.l d0
 	rts
 	
 stop:	addi.w #1,d0
 	ext.l d0
 	divu.w #40,d0
 	ext.l d0
 	rts