Building Boxes

You have a cubic storage area where the width, length, and height are all equal to n. You are given n cubical boxes, where the ith box has a side length of i. You want to build a stack of boxes that is as tall as possible, but you can only place a box on top of another box if the side length of the box on top is strictly smaller than the side length of the box underneath.

Write a function to calculate the maximum height of the stack that you can build.