import sys 
lamda = [4] * 13
xmaxUser1039 = [0,0,0,0,0,0,0,0,0,0,0,0,0]
surplusEnergyUser1039 = [3.820,0,0,0,0,0,0,0,0,0,0,0,0]
lamdaUser1039 = lamda
pricesUser1039 = [5.1,0,0,0,0,0,0,0,0,0,0,0,0]
p = float(sys.argv[1])
t = int(sys.argv[2])
x = (pricesUser1039[t] - p)/lamdaUser1039[t]
if x < 0:
	x = 0
elif x > xmaxUser1039:
	x = xmaxUser1039
print(str(x))
sys.stdout.flush()