// editor4
#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.discount
    }
}