using System;

namespace Harder_checks
{
    class Program
    {
        static void Main(string[] args)
        {
            string product = Console.ReadLine();
            string city = Console.ReadLine();
            int quantity = int.Parse(Console.ReadLine());

            double price = 0;

            if ((product == "coffee") && (city == "Sofia"))
            {
                price = 0.5;
                Console.WriteLine(quantity * price);
            }
            if ((product == "coffee") && (city == "Plovdiv"))
            {
                price = 0.4;
                Console.WriteLine(quantity * price);
            }
            if ((product == "coffee") && (city == "Varna"))
            {
                price = 0.45;
                Console.WriteLine(quantity * price);
            }
            if ((product == "water") && (city == "Sofia"))
            {
                price = 0.8;
                Console.WriteLine(quantity * price);
            }
            if ((product == "water") && (city == "Plovdiv"))
            {
                price = 0.7;
                Console.WriteLine(quantity * price);
            }
            if ((product == "water") && (city == "Varna"))
            {
                price = 0.7;
                Console.WriteLine(quantity * price);
            }
            if ((product == "beer") && (city == "Sofia"))
            {
                price = 1.2;
                Console.WriteLine(quantity * price);
            }
            if ((product == "beer") && (city == "Plovdiv"))
            {
                price = 1.15;
                Console.WriteLine(quantity * price);
            }
            if ((product == "beer") && (city == "Varna"))
            {
                price = 1.1;
                Console.WriteLine(quantity * price);
            }
            if ((product == "sweets") && (city == "Sofia"))
            {
                price = 1.45;
                Console.WriteLine(quantity * price);
            }
            if ((product == "sweets") && (city == "Plovdiv"))
            {
                price = 1.3;
                Console.WriteLine(quantity * price);
            }
            if ((product == "sweets") && (city == "Varna"))
            {
                price = 1.35;
                Console.WriteLine(quantity * price);
            }
            if ((product == "peanuts") && (city == "Sofia"))
            {
                price = 1.6;
                Console.WriteLine(quantity * price);
            }
            if ((product == "peanuts") && (city == "Plovdiv"))
            {
                price = 1.5;
                Console.WriteLine(quantity * price);
            }
            if ((product == "peanuts") && (city == "Varna"))
            {
                price = 1.55;
                Console.WriteLine(quantity * price);
            }



        }
    }
}