Tallest Billboard

You are installing a billboard and want to maximize its height. The billboard has two steel supports that are one unit apart. Each support can be of varying heights. You have a list of integers rods where rods[i] represents the height of the ith steel support.

You can order any number of rods (or none) to place on the two supports, such that the total height of the billboard is maximized. Return the maximum height of the billboard.