The following is a MATLAB function to calculate begin mathsize $20$px style sum from i equals $1$ to n of $2$ A subscript i end style, where n is the length of the vector begin mathsize $20$px style A with rightwards harpoon with barb upwards on top equals left square bracket A subscript $1$ comma space A subscript $2$ comma space... space comma space A subscript n right square bracket end style. Fill in the blank to complete the code. Do NOT type space in your answer. Note that MATLAB is case sensitive$.$

function s $=$ sumUp$($A$)$

$\%$ A is a vector here.

s $=0$;

for i $=1$:length$($A$)$

s $=$ s $+\_\_\_\_\_\_$;

end

end