using System;

namespace P04.BottleDeposit
{
    class Program
    {
        static void Main(string[] args)
        {
            int halfLiterBottles = int.Parse(Console.ReadLine());
            int oneLiterBottles = int.Parse(Console.ReadLine());

            double totalSum = halfLiterBottles * 0.1 + oneLiterBottles * 0.25;

            Console.WriteLine($"{totalSum:F2}");
        }
    }
}