#include <stdio.h>
int main()
{
int gongzi;
double shui,sum;
scanf("%d",&gongzi);
if(gongzi>4500){
sum=0.20*(gongzi-1600.00);
}else if(gongzi>3500&&gongzi<=4500){
sum=0.15*(gongzi-1600.00);
}else if(gongzi>2500&gongzi<=3500){
sum=0.10*(gongzi-1600.00);
}else if(gongzi>1600&gongzi<=2500){
sum=0.05*(gongzi-1600.00);
}else{
sum==0;
}
printf("%.2f",sum);
return 0;
}