import java.util.Scanner;

public class HelloWorld {
    public static void main(String[] args) {

      Scanner scan = new Scanner(System.in);
double input = scan.nextDouble();
if (input<20000) System.out.printf("%.2f",0.);
else if (input < 40000) System.out.printf("%.2f",input*0.1);
else if (input<60000)System.out.printf("%.2f",input*0.2);
    else System.out.printf("%.2f",input*0.3);}

}