using System;               

public class Program

{

    public static void Main()

    {

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

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

        Lice(a,b);

        Lice1(a,b);

​

    }

    static void Lice(double a, double b)

    {

        Console.WriteLine(a*b/2);

​

    }

    static double Lice1(double a, double b)

    {

        return(a*b/2);

    }}

​

​