using System;

public class Program

{

    public static void Main()

    {

       double a, b, c;

       double s = 0;

        Console.WriteLine("podaj bok A")

        a = double.Parase(Console.ReadLine());

        Console.WriteLine("podaj bok B")

        b = double.Parase(Console.ReadLine());

        Console.WriteLine("podaj bok C")

        c = double.Parase(Console.ReadLine());

        if((a+b>c) && (a+c>b) && (b+c>a)

        {

           s=Math.Sqrt((a+b+c)*(a+b-c)*(a-b+c)*(-a+b+c))/4;

            Console.WriteLine("Pole: {0:f2}", s);

        }

           else

           Console.WriteLine("Nie da sie zbudowac trojkata");

    }

}