using System;
using System.IO;
using System.Linq;

namespace ConsoleApp4
{
    class Program
    {
        static void Main()
        {
            var N = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var x = N[0];
            var y = N[1];
            var z = N[2];

            var a = (Math.Abs(x - y) - N[2]) / 2;
            var b  = Math.Abs(a);

            var max = Math.Max(x, y);
            
            Console.WriteLine(b + max);

        }
    }
}