using System;

public class Program

{

    public static void Main()

    {

        double Lmeters = double.Parse(Console.ReadLine());

        double Wmeters =double.Parse(Console.ReadLine());

        double A = double.Parse(Console.ReadLine());

        double Acm = A*100;

        double areaHall = (Lmeters*100)*(Wmeters*100);

        double areaA = Acm*Acm;

        double areaBench =  areaHall/10;

        double freeArea = areaHall-areaA-areaBench;

        double dancers = freeArea/(40+7000);

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

    }

}