using System;

namespace _11._Dance_hall
{
    class Program
    {
        static void Main(string[] args)
        {
            Double Lenght = Double.Parse(Console.ReadLine());
            Double Width = Double.Parse(Console.ReadLine());
            Double WordrobeSide = Double.Parse(Console.ReadLine());

            Double hallArea = (Lenght * 100) * (Width * 100);
            Double wordrobeArea = WordrobeSide * WordrobeSide;
            Double benchArea = hallArea / 10;
            Double freeHallSpace = hallArea - wordrobeArea - benchArea;
            Double dancers = freeHallSpace / (40 + 7000);

            Console.WriteLine(Math.Floor(dancers));
        }
    }
}