import java.util.*;

interface Item {
	double getValue();
}


class Book implements Item {
	private double price;
	public double getValue() {
		return price;
	}
}

public class Cart {
	ArrayList<Item> items;
	public double getTotal() {
		double total = 0;
		for(Item item: items) {
			total += item.getValue();
		}
		return total;
	}
}