import sys 
lamda = [4] * 13
xmaxUser1028 = [0,0,0,0,0,0,0,0,0,0,0,0,0]
surplusEnergyUser1028 = [2.732,0,0,0,0,0,0,0,0,0,0,0,0]
lamdaUser1028 = lamda
pricesUser1028 = [8.1,0,0,0,0,0,0,0,0,0,0,0,0]
p = float(sys.argv[1])
t = int(sys.argv[2])
x = (pricesUser1028[t] - p)/lamdaUser1028[t]
if x < 0:
	x = 0
elif x > xmaxUser1028:
	x = xmaxUser1028
print(str(x))
sys.stdout.flush()