#include<stdio.h>
struct Order {
    int quantity;
    float price_per_book;
    union{
        float discountRate;
        int discountPercent;
    }disc;
    float total_cost;
};
int main() {
struct Order order;
order.price_per_book = 100.0f;
scanf("%d",&order.quantity);
if(order.quantity<0) {
    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.discountRate=0.15;
}
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 * (0.1f - order.disc.discountRate);
printf("%.2f",order.total_cost);
return 0;