using System;

namespace DanceHall
{
    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 space = l * w - (l * w / 10) - a * a;
            int dancers = (int)(space / 0.7040);
            Console.WriteLine(dancers);
        }
    }
}