import java.util.Scanner;
public class Main{
    public static void main(String[] args){
        Scanner myscanner = new Scanner(System.in);
        int a = myscanner.nextInt();
        double sum = 0;
        if (a <= 150) {
            sum = a * 0.4463;
        }else{
            sum = 150 * 0.4463;
        }
        if (a > 151 && a <= 400) {
            sum = sum + (a - 150) * 0.4663;
        }
        if (a >= 401) {
            sum = sum + 250 * 0.4663 +  (a - 400) * 0.5663;
        }
        System.out.println((int)(sum * 10)/10.0);
    }
}