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

namespace template
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            double[] x = Console.ReadLine().Split().Select(double.Parse).ToArray();
            Console.WriteLine(n % 2 == 0 ? (x[n / 2 - 1] + x[n / 2]) / 2 : x[(n - 1) / 2]);
        }
    }
}