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

namespace Yukicoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var line = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
            var right = line.Max();
            var left = line.Min();
            while (right - left > 1)
            {
                var mid = (right + left)/2;
                var sum = 0;
                for (int i = 0; i < line.Length; i++)
                {
                    if (line[i] >= mid)
                    {
                        sum += (line[i] - mid)/2;
                    }
                    else
                    {
                        sum -= mid - line[i];
                    }
                }
                if (sum >= 0)
                {
                    left = mid;
                }
                else
                {
                    right = mid;
                }
            }
            Console.WriteLine(left);
        }
    }
}