Scrooge McDuck has 100 golden coins on his office table. He wants to distribute them into 10 piles so that no two piles contain the same amount of coins. And moreover, no matter how you divide any of the piles into two smaller piles among the resulting 11 piles there will be two with the same amount of coins. Sounds impossible? Try to find a suitable example. Scrooge spent a while on working out this question, maybe he will even give you a penny.