import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int a=sc.nextInt();
		double b=a;
		if(a<=150) {
			b=a*0.4463;
		}else {
			if(a>=151&&a<=400) {
				b=150*0.4463;
				b+=(a-150)*0.4663;
			}else {
				b=150*0.4463;
				b+=(a-250)*0.4663;
				b+=(a-400)*0.5663;
			}
		}
		System.out.printf(String.format("%.1f", b));
	}
	}