text: """
  Pooja would like to withdraw X $US from an ATM. The cash machine will only accept the transaction if X is a multiple of 5, and Pooja's account balance has enough cash to perform the withdrawal transaction (including bank charges). For each successful withdrawal the bank charges 0.50 $US. Calculate Pooja's account balance after an attempted transaction.
  
  Input
  Positive integer 0 < X <= 2000 - the amount of cash which Pooja wishes to withdraw.
  
  Nonnegative number 0<= Y <= 2000 with two digits of precision - Pooja's initial account balance.
  
  Output
  Output the account balance after the attempted transaction, given as a number with two digits of precision. If there is not enough money in the account to complete the transaction, output the current bank balance.
  
  Example - Successful Transaction
  Input:
  30 120.00
  
  Output:
  89.50
  Example - Incorrect Withdrawal Amount (not multiple of 5)
  Input:
  42 120.00
  
  Output:
  120.00
  Example - Insufficient Funds
  Input:
  300 120.00
  
  Output:
  120.00
  """
  
  def withdrawMoney() : 
      wamount, totalamount = list(map(float, input().split()))
      
      dispense = wamount + 0.5
  
      if wamount%5 == 0 and dispense <= totalamount : 
          return float("{:.3f}".format(totalamount - dispense))
      else : 
          return float("{:.3f}".format(totalamount))
  
  if __name__ == "__main__" : 
      print(withdrawMoney())