// editor4
#include<stdio.h>
struct Order
{
    int quality;
    float price_per_bok;
    union
    {
        float discountRate;
        int discountPercent;
    }disc;
    float total_cost;
};
int main()
{
    struct Order order;
    order.price_per_book;
    scanf("%d",&order.quantity);
    if(order.quantity)
    {
        printf("Invalid input");
        return 0;
    }
    if(order.quantity>=1 && order.quantity<=5)
    {
        order.disc.discountRate=0.10f;
    }
    else if(order.quantity>=6 && order.quantity<=10)
    {
        order.disc.discoountRate=0.15f;
    }
    else if(order.quantity>10)
    {
        order.disc.discountRate=0.20f;
    }
    else
    {
        order.disc.discountRate=0.0f;
    }
    float gross= order.quantity*order.price_per_book;
    order.total_cost*gross*(1.0f-order.disc.discountRate);
    printf("%.2f",order.total_cost);
    return 0;
}