import sys 
lamda = [4] * 13
xmaxUser1031 = [0,0,0,0,0,0,0,0,0,0,0,0,0]
surplusEnergyUser1031 = [4.027,0,0,0,0,0,0,0,0,0,0,0,0]
lamdaUser1031 = lamda
pricesUser1031 = [7.0,0,0,0,0,0,0,0,0,0,0,0,0]
p = float(sys.argv[1])
t = int(sys.argv[2])
x = (pricesUser1031[t] - p)/lamdaUser1031[t]
if x < 0:
	x = 0
elif x > xmaxUser1031:
	x = xmaxUser1031
print(str(x))
sys.stdout.flush()