x=int(input())
if x <=10:
    p=x*0.8+0.2
    print("%.2f"%p)
elif x<=20:
    p=(x-10)*0.75+10*0.8+0.2
    print("%.2f"%p)
elif x<=30:
    p=(x-20)*0.7+10*0.75+10*0.8+0.2
    print("%.2f"%p) 
else:   
    print("Fail")