import sys 
lamda = [4] * 13
xmaxUser1022 = [0,0,0,0,0,0,0,0,0,0,0,0,0]
surplusEnergyUser1022 = [3.920,0,0,0,0,0,0,0,0,0,0,0,0]
lamdaUser1022 = lamda
pricesUser1022 = [6.5,0,0,0,0,0,0,0,0,0,0,0,0]
p = float(sys.argv[1])
t = int(sys.argv[2])
x = (pricesUser1022[t] - p)/lamdaUser1022[t]
if x < 0:
	x = 0
elif x > xmaxUser1022:
	x = xmaxUser1022
print(str(x))
sys.stdout.flush()