$11i{r}_2$

start: in $r1,$ #Read an input value into register $r1$

# Check if the entered number is negative or positive

sub Check if $r_1$ is negative$)$

bge $r38$updateHighest #update highest number

blt $r3$ &start #If $r1$ is positive, go back to start to keep asking

bge $r38$printHigh #If $r_1$ is negative, go to printHigh to output and stop

updateHighest:

add $r_2{r}_2{r}_1$

printHigh: out $r_2$ #Output the entered number $($highest positive or zero$)$

$.$ halt $,$ #Halt the program