import sys 
lamda = [4] * 13
xmaxUser1029 = [0,0,0,0,0,0,0,0,0,0,0,0,0]
surplusEnergyUser1029 = [3.512,0,0,0,0,0,0,0,0,0,0,0,0]
lamdaUser1029 = lamda
pricesUser1029 = [7.2,0,0,0,0,0,0,0,0,0,0,0,0]
p = float(sys.argv[1])
t = int(sys.argv[2])
x = (pricesUser1029[t] - p)/lamdaUser1029[t]
if x < 0:
	x = 0
elif x > xmaxUser1029:
	x = xmaxUser1029
print(str(x))
sys.stdout.flush()