using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _14IntegerToHexAtBinary
{
    class IntegerToHexAtBinary
    {
        static void Main(string[] args)
        {
            Console.Write(" a=  ");
            var a = Double.Parse(Console.ReadLine());
            Console.Write(" h=  ");
            var h = Double.Parse(Console.ReadLine());
            var area = (a * h / 2);
            var result = Math.Round(area, 2);
            Console.WriteLine(result);
        }
    }

}