output_description: Print the amount of change as an integer.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
attempt: n = int(input()) - 1
  k = list(str(n))
  kk = int(k[0])
  print((kk + 1) * 1000 - n - 1)
  
problem_description: Statement
  
  We will buy a product for N yen (the currency of Japan) at a shop.
  
  If we use only 1000-yen bills to pay the price, how much change will we
  receive?
  
  Assume we use the minimum number of bills required.
samples: [{"input": "1900", "output": "100\n    \n\nWe will use two 1000-yen bills to pay the price and receive 100 yen in change.\n\n* * *"}, {"input": "3000", "output": "0\n    \n\nWe can pay the exact price."}]