import java.util.Scanner;

public class SmallShop {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String products = scanner.nextLine().toLowerCase();
        String town = scanner.nextLine().toLowerCase();
        double quantity = Double.parseDouble(scanner.nextLine());

        double productPrice = 0;

        if (town.equals("sofia")){
            if (products.equals("coffee")){
                productPrice = 0.5;
            }else if (products.equals("water")){
                productPrice = 0.8;
            }else if (products.equals("beer")){
                productPrice = 1.2;
            }else if (products.equals("sweets")){
                productPrice = 1.45;
            }else if (products.equals("peanuts")){
                productPrice = 1.6;
            }
        }else if (town.equals("plovdiv")){
            if (products.equals("coffee")){
                productPrice = 0.4;
            }else if (products.equals("water")){
                productPrice = 0.7;
            }else if (products.equals("beer")){
                productPrice = 1.15;
            }else if (products.equals("sweet")){
                productPrice = 1.3;
            }else if (products.equals("peanuts")){
                productPrice = 1.5;
            }
        }else if (town.equals("varna")){
            if (products.equals("coffee")){
                productPrice = 0.45;
            }else if (products.equals("water")){
                productPrice = 0.7;
            }else if (products.equals("beer")){
                productPrice = 1.1;
            }else if (products.equals("sweets")){
                productPrice = 1.35;
            }else if (products.equals("peanuts")){
                productPrice = 1.55;
            }
        }
        double total = quantity * productPrice;
        System.out.printf("%.2f", total);

    }
}