#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.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 * (1.0f - order.disc.discountRate);
    printf("%.2f",order.total_cost);
    return 0;
}