import sys 
lamda = [4] * 13
xmaxUser1026 = [0,0,0,0,0,0,0,0,0,0,0,0,0]
surplusEnergyUser1026 = [0.556,0,0,0,0,0,0,0,0,0,0,0,0]
lamdaUser1026 = lamda
pricesUser1026 = [7.6,0,0,0,0,0,0,0,0,0,0,0,0]
p = float(sys.argv[1])
t = int(sys.argv[2])
x = (pricesUser1026[t] - p)/lamdaUser1026[t]
if x < 0:
	x = 0
elif x > xmaxUser1026:
	x = xmaxUser1026
print(str(x))
sys.stdout.flush()