#include<stdio.h>
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;
}