using System;

public class Program

{

    public static void Main()

    {

        var product = Console.ReadLine().ToLower();

        var grad = Console.ReadLine().ToLower();

        var kolichestvo = double.Parse(Console.ReadLine());

        if (grad == "sofia")

        {

            if (product == "coffee")

            { Console.WriteLine(0.50*kolichestvo);}

        }

        if (grad == "varna")

        {

            if (product == "coffee")

            { Console.WriteLine(0.40*kolichestvo);}

        }

    }

}