output_description: Print the amount you have left after shopping.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      X
      A
      B
attempt: i = lambda: int(input())
  print((i() - i()) % i())
  
problem_description: Statement
  
  You went shopping to buy cakes and donuts with X yen (the currency of Japan).
  
  First, you bought one cake for A yen at a cake shop. Then, you bought as many
  donuts as possible for B yen each, at a donut shop.
  
  How much do you have left after shopping?
samples: [{"input": "1234\n    150\n    100", "output": "84\n    \n\nYou have 1234 - 150 = 1084 yen left after buying a cake. With this amount, you\ncan buy 10 donuts, after which you have 84 yen left.\n\n* * *"}, {"input": "1000\n    108\n    108", "output": "28\n    \n\n* * *"}, {"input": "579\n    123\n    456", "output": "0\n    \n\n* * *"}, {"input": "7477\n    549\n    593", "output": "405"}]