"I was carefully cleaning up the fragments of this broken window with my three friends.

I picked up the first three pieces. My friends followed in turn, each picking up three more pieces than whoever went before them.

In the end, there were still three fragments on the floor. How many pieces of glass were there to begin with?" Provide your response in exactly 7 paragraphs (separated nearby paragraphs with 3 aterisk symbols ***).
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