As you play Mario & Luigi: Brothership, you’ll eventually discover that Ellow is missing, and you must hunt down the Extension Corps. You’ll start this quest on Lottacoins Island in Building 1F. You have to get to the roof, but there is no direct passage there, and looking around for a final set of stairs will leave you stumped. The real way to get to the roof involves finding a pipe puzzle room and using it to get to the roof.
https://screenrant.com/mario-luigi-brothership-how-to-solve-lottacoins-island-tubes-puzzle/
