using System;

public class Program

{

    public static void Main()

    {

        var product = Console.ReadLine();

        var town = Console.ReadLine();

        double quality = 0;

        var n = int.Parse(Console.ReadLine());

        double pay = 0;

        if(product == "coffee")

        {

            if(town == "sofia"){

            quality = 0.5;

            }

            if(town == "plovdiv"){

            quality = 0.4;

            }

            if(town == "varna"){

            quality = 0.45;

            }

            pay = n*quality;

            Console.WriteLine(pay);

        }

        if(product == "water")

        {

            if(town == "sofia"){

            quality = 0.8;

            }

            if(town == "plovdiv"){

            quality = 0.7;

            }

            if(town == "varna"){

            quality = 0.7;

            }

                        pay = n*quality;

            Console.WriteLine(pay);

        }

        if(product == "beer")

        {

            if(town == "sofia"){

            quality = 1.20;

            }

            if(town == "plovdiv"){

            quality = 1.15;

            }

            if(town == "varna"){

            quality = 1.10;

            }

                        pay = n*quality;

            Console.WriteLine(pay);

        }

        if(product == "sweets")

        {

            if(town == "sofia"){

            quality = 1.45;

            }

            if(town == "plovdiv"){

            quality = 1.30;

            }

            if(town == "varna"){

            quality = 1.35;

            }

                        pay = n*quality;

            Console.WriteLine(pay);

        }

        if(product == "peanuts")

        {

            if(town == "sofia"){

            quality = 1.60;

            }

            if(town == "plovdiv"){

            quality = 1.50;

            }

            if(town == "varna"){

            quality = 1.55;

            }

                        pay = n*quality;

            Console.WriteLine(pay);

        }

    }

}