#include<stdio.h>
int main()
{
	double n,sum;
	scanf("%lf",&n);
	if(n<=150)
	{
		sum=0.4463*n;
	}
	else
	{
		sum=0.4463*150;
		n-=150;
		if(n<=250)
		{
			sum+=0.4663*n;
		}
		else
		{
			sum+=0.4663*250;
			n-=250;
			sum+=n*0.5663*n;
		}
	}
	sum=int((sum*10)+0.5)/10.0;
	printf("%.1f",sum);
}