using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("enter tzele1");

        double a = int.Parse(Console.ReadLine());

        Console.WriteLine("enter tzele2");

        double b = int.Parse(Console.ReadLine());

        Console.WriteLine("enter tzele3");

        double c = int.Parse(Console.ReadLine());

        double hekef = a+b+c;

        double p = hekef/2;

        double shetah = Math.Sqrt(p*(p-a)*(p-b)*(p-c));

        Console.WriteLine("shetah hamesulash is:" +shetah);

    }

}