using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace VeggieFruits
{
    class Program
    {
        static void Main(string[] args)
        {
            var priceVeggie = Double.Parse(Console.ReadLine());
            var priceFruit = Double.Parse(Console.ReadLine());
            int kiloVeggie = int.Parse(Console.ReadLine());
            int kiloFriut = int.Parse(Console.ReadLine());



            var revVeggie = priceVeggie * kiloVeggie;
            var revFruit = priceFruit * kiloFriut;
            double revTotal = revVeggie + revFruit;
            double revEur = Math.Round(revTotal / 1.94, 2);
            Console.WriteLine(revEur);




        }
    }
}