#include <stdio.>
int main()
{
 int units;
 float bill =0.0;
 scanf("%d",&units);
 if(units < 0) {
     printf("Invalid input");
     return 0;
 }
 if(units <= 100) {
     bill = units *0.10;
 }
 else if( units <= 200) {
     bill =(100*0.10)+(units - 100)*0.15;
 }
 else {
     bill=(100*0.10)+(100*0.15)+(units -200)*0.20;
 }
 printf("%.2f",bill);
 return 0;
}