using System;

namespace DanceRoomProblem
{
    class Program
    {
        static void Main(string[] args)
        {
           double L = double.Parse(Console.ReadLine());
           double W = double.Parse(Console.ReadLine());
           double A = double.Parse(Console.ReadLine());

            double areaRoom = L * W;
            //Console.WriteLine(areaRoom);

            double areaBench = areaRoom / 10;
            //Console.WriteLine(areaBench);

            double areaWaredrobe = A * A;
            //Console.WriteLine(areaWaredrobe);

            double usefulArea = areaRoom - areaBench - areaWaredrobe;
            //Console.WriteLine(usefulArea);

            double spaceNeededForDancer = 0.704;
            //Console.WriteLine(spaceNeededForDancer);

            double totalNumberOfDancers = Math.Floor(usefulArea / spaceNeededForDancer);

            Console.WriteLine(totalNumberOfDancers);




        }
    }
}