import sys 
lamda = [4] * 13
xmaxUser1024 = [0,0,0,0,0,0,0,0,0,0,0,0,0]
surplusEnergyUser1024 = [2.857,0,0,0,0,0,0,0,0,0,0,0,0]
lamdaUser1024 = lamda
pricesUser1024 = [9.1,0,0,0,0,0,0,0,0,0,0,0,0]
p = float(sys.argv[1])
t = int(sys.argv[2])
x = (pricesUser1024[t] - p)/lamdaUser1024[t]
if x < 0:
	x = 0
elif x > xmaxUser1024:
	x = xmaxUser1024
print(str(x))
sys.stdout.flush()