How to determine value of closest to but not greater than an input value in an Array

I am having trouble figuring out how to determine the last element of the print statement.  For array A(N) and input element ARG, what kind of algorithm is needed to determine which element of A(N) is closest to but not greater than ARG?  I've gotten this far but can't find anything in my course manual that describes this situation.


If A(1) < ARG > A(N) then
        CODE = 2
        Print ARG, CODE, A(N) that is closest to but not greater than ARG