Document Classes ⇒ Beamer - Demonstration in many pages

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Hi,

I want to use a demonstration box. But my demo is too long, then I need to write it in many pages. But at the bottom of each demo box, it appears a white square, then if I create a demo box in each page, it will be a bit weird ...

In that case, how I can write in a demo box along many pages ?

Thank you in advance.