I'm stupid," Leo mumbled. "Pi would expand outward, because it's infinite."

He reversed the order of the numbers, starting in the center and working toward the edge. When he aligned the last ring, something inside the sphere clicked. The door swung open.

Leo beamed at his friends. "That, good people, is how we do things in Leo World. Come on in!"

"I hate Leo World," Frank muttered.

Hazel laughed.

Autore: Rick Riordan