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
# -*- coding: utf-8 -*-
"""
Created on Mon Jul 04 12:49:36 2016

@author: Seba
"""

# -*- coding: utf-8 -*-
"""
Created on Mon Jul 04 11:23:17 2016

@author: Seba
"""
import sys

def solve(x, b):
    if x % 5 != 0:
        return b
    
    real_x = float(x) + 0.5
    if real_x > b:
        return b 
    else:
        return b - real_x

inp = sys.stdin.readline().split()
x = int(inp[0])
b = float(inp[1])
print("%.2f"%solve(x,b))

#tests = []
#for t in range(T):
#    sys.stdin.readline()
#    tests.append([int(i) for i in sys.stdin.readline().split()])
#    
#for test in tests:    
#    print solve(test)