using System;
class Haromszog
{
	public static double szamitTerulet(double alap, double magassag) {
		if(alap <= 0 || magassag <= 0) {
			throw new ArgumentException();
		}
		return (alap * magassag) / 2;
	}
	public static void Main() {
		Console.WriteLine("Hi");
	}
}