using static System.Math;
using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = int.Parse(line[0]);
        var b = int.Parse(line[1]);
        var c = int.Parse(line[2]);
        var dif = Abs(a - b);
        if (c < dif) Console.WriteLine(Min(a, b) + c);
        else Console.WriteLine(Max(a, b) + (c - dif) / 2);
    }
}