town = input().lower()
product = input().lower()
quantify = float(input())
price = -1.0
if town == 'Sofia':
    if product == 'coffee':
        price = 0.5 * quantify
    elif product == 'water':
        price = 0.8 * quantify
    elif product == 'beer':
        price = 1.20 * quantify
    elif product == 'sweets':
        price = 1.45 * quantify
    elif product == 'peanuts':
        price = 1.60 * quantify

elif town == 'Plovdiv':
    if product == 'coffee':
        price = 0.40 * quantify
    elif product == 'water':
        price = 0.70 * quantify
    elif product == 'beer':
        price = 1.15 * quantify
    elif product == 'sweets':
        price = 1.30 * quantify
    elif product == 'peanuts':
        price = 1.50 * quantify

elif town == 'Varna':
    if product == 'coffee':
        price = 0.45 * quantify
    elif product == 'water':
        price = 0.70 * quantify
    elif product == 'beer':
        price = 1.10 * quantify
    elif product == 'sweets':
        price = 1.35 * quantify
    elif product == 'peanuts':
        price = 1.55 * quantify
print("{0:.2f}".format(price))