#include<stdio.h>
int main(
    {
        int units;
        double bill=0.0;
        if(scanf("%d",&units)!=1||units<0)
        {
            printf("Invalid input");
            return 0;
        }
        if(units<=100)
        {
            bill=units*0.10;
        }
        else if(units<=200)
        {
            bil=100*0.10+(units-100)*0.15;
        }
        else{
            bill=100*0.10+100*0.15+(units-200)*0.20;
        }
        printf("%.2f\n",bill);
        return 0;
        
    }