n = input()
n = int(n)
if n >= 30:
    print("%.1f"%(1*n))    
elif 20 <= n <= 29:
    print("%.1f"%(1.2*n))
elif 10 <= n <= 19:
    print("%.1f"%(1.5*n))
elif n <= 10:
    print("%.1f"%(1.8*n))
    

/**************************************************************
	Problem: 1304
	User: xiaomingze
	Language: Python
	Result: Accepted
	Time:246 ms
	Memory:34480 kb
****************************************************************/