using System;

public class Program
{
    public static void Main()
    {
        int a = int.Parse(Console.ReadLine());
        int b = int.Parse(Console.ReadLine());
        int c = int.Parse(Console.ReadLine());

        if(a>0 && b > 0  && c > 0)
        {
        if(a + b > c && b+c >a && a+c>b)
        {
        int area = a + b + c;
        double lice = Math.Sqrt(area / 2 * ((area/2) - a)*((area/2)-b)*((area/2)-c));
        Console.WriteLine(lice);

        }
            else {
            Console.WriteLine("Nqma triAgAlNik");
            }
        }
    }
}