try:
c=0.50
X=int(input())
Y=float(input())
Y=round(Y,2)
if X in range(0,2001):
if 0<Y<2001:
D=Y+c
if X%5==0 and X<=D:
Y=Y-X-c
print(round(Y,2))
else:
print(round(Y,2))
else:
print(‘Invalid Input’)
else:
print(‘Invalid’)
except:
pass