lirun=int(raw_input('input'))
if lirun <=10:
jiangjin=lirun * 0.1
print 'your jinagjin is',jiangjin
elif (lirun> 10 )and (lirun <=20):
jiangjin=10*0.1+(lirun-10)*0.075
print jiangjin
elif (lirun>20) and (lirun <=40):
jiangjin=0.05*(lirun-20)
print jiangjin