using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Please enter the length of the first side");

        double L1 = float.Parse(Console.ReadLine());

        Console.WriteLine("Please enter the length of the second side");

        double L2 = float.Parse(Console.ReadLine());

        Console.WriteLine("Please enter the length of the third side");

        double L3 = float.Parse(Console.ReadLine());

        double S;

        S = ( L1 + L2 + L3) / 2;

            double A;

        A = Math.Sqrt(S*(S-L1)*(S-L2)*(S-L3));

        Console.WriteLine("The area of this triangle is {0}", A );

    }

}