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: import functools
  
  import os
  
  INF = float("inf")
  
  
  def inp():
      return int(input())
  
  
  def inpf():
      return float(input())
  
  
  def inps():
      return input()
  
  
  def inl():
      return list(map(int, input().split()))
  
  
  def inlf():
      return list(map(float, input().split()))
  
  
  def inls():
      return input().split()
  
  
  def debug(fn):
      if not os.getenv("LOCAL"):
          return fn
  
      @functools.wraps(fn)
      def wrapper(*args, **kwargs):
          print(
              "DEBUG: {}({}) -> ".format(
                  fn.__name__,
                  ", ".join(
                      list(map(str, args))
                      + ["{}={}".format(k, str(v)) for k, v in kwargs.items()]
                  ),
              ),
              end="",
          )
          ret = fn(*args, **kwargs)
          print(ret)
          return ret
  
      return wrapper
  
  
  x = inp()
  a = inp()
  b = inp()
  x -= a
  print(x % b)
  
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"}]