What is the task performed by the following algorithm?

A: a bit vector $($an array storing only $1\text{'}$s and $0\text{'}$s$)$

pos: highest index of array $A$

function $,$ pos$)$

if $(pos<mi\; id="EditorElement\_677289"></mi><mi\; id="EditorElement\_677291">)</mi>$

return $$

if $($pos$0$ or pos $-1$