# Inspired by my little cousin - the greatest artist of all time

**Geometry**Level 5

One of the dreams of my little cousin is to become a great architect. His parents have given him many unit cube blocks to hone his skills.

One time, I noticed that he built 2 distinct square-based cuboids, in which exactly half of the cubes used could be seen from the outside.

What is the total number of cubes that he used?

Note: Cubes that are touching the ground, but not on the outside, canot be side. As an explicit example, the smallest building that hides at least 1 cube, has a square base of 3, and a height of 2. Exactly 1 cube not visible.

Special thanks to: Michael Mendrin

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