lw	0	8	neg1	load reg8 with -1
	lw	0	5	four	load reg5 with 4
loop	add	5	8	5	reg5 <- reg5 + reg8 (reg5 decremented)
	beqz	5	done		if reg5=0, go to done
	j	loop
done	halt
neg1	.fill	-1
four	.fill	4