Arrays are commonly used in conjunction with repeatedly if$,$ in order to iterate over the array. Iteration allows us to access all the elements in the array one$-$by$-$one, and manipulate them as needed. For example, consider the following code:

a :$=$ make$\_$array$(4,5,6)$

x :$=0$

s :$=0$

repeatedly if $($x $<3)$ then:

s :$=$ s $+$ a$[$x$]$

x :$=$ x $+1$

Variable x is used as an index into the array held in a$,$ which initially starts at $0($specifically with x :$=0).$ The condition of the repeatedly if checks to see that x is less than $3.$ This is significant, as the largest valid index for the array in a is $2,$ and $2$ is the largest integer is that less than $3.$ Lastly, each time the code underneath the repeatedly if is executed, the value in x is incremented by $1($specifically with x :$=$ x $+1).$ With this in mind, the above code will iterate through every element of the array in a$,$ starting from the value at index $0$ and ending with the value at index $2.$ Upon each iteration, the value of the current element of the array is added to a rolling sum of the array $($specifically with s :$=$ s $+$ a$[$x$]).$ All of this ultimately means that s will hold the sum of the elements in the array once this code completes, so s will ultimately hold the value $15$ once this code is done executing.

Consider the following related code:

a :$=$ make$\_$array$(5,2,1,2)$

x :$=0$

r :$=1$

repeatedly if $($x $<4)$ then:

r :$=$ r $*$ a$[$x$]$

x :$=$ x $+1$

What value will r hold once the above code finishes executing?