using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var input = Console.ReadLine().Split().Select(int.Parse).ToArray();
        var X = input[0];
        var Y = input[1];
        var Z = input[2];

        var max = Math.Max(X, Y);
        var diff = Math.Abs(X - Y);

        if (Z >= diff) Console.WriteLine(max + (Z - diff) / 2);
        else Console.WriteLine(Math.Min(X, Y) + Z);
    }
}