SandBox

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

namespace Sandbox
{
    class Program
    {
        static void Main(string[] args)
        {
            double width = double.Parse(Console.ReadLine());
            double lenght = double.Parse(Console.ReadLine());
            double sandPrice = double.Parse(Console.ReadLine());
            double boardPrice = double.Parse(Console.ReadLine());


            double sandArea = (width - 0.4) * (lenght - 0.4);
            double boardArea = width * lenght - sandArea;
            double sandNeeded = Math.Ceiling(sandArea * 20);
            double boardsNeeded = Math.Ceiling(boardArea / 0.44);
            double totalPrice = sandNeeded * sandPrice + boardsNeeded * boardPrice;

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