import sys 
lamda = [4] * 13
xmaxUser1027 = [0,0,0,0,0,0,0,0,0,0,0,0,0]
surplusEnergyUser1027 = [3.557,0,0,0,0,0,0,0,0,0,0,0,0]
lamdaUser1027 = lamda
pricesUser1027 = [10.8,0,0,0,0,0,0,0,0,0,0,0,0]
p = float(sys.argv[1])
t = int(sys.argv[2])
x = (pricesUser1027[t] - p)/lamdaUser1027[t]
if x < 0:
	x = 0
elif x > xmaxUser1027:
	x = xmaxUser1027
print(str(x))
sys.stdout.flush()