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

namespace yukicoder
{
    public class Program
    {
        public static void Main()
        {
            var n = int.Parse(Console.ReadLine());
            var a = Console.ReadLine().Split().Select(x => long.Parse(x)).ToList();
            long s = 0;
            for(var i = 0; i <= n; i++)
            {
                var j = 0;
                long t = 0;
                while (j < i)
                {
                    t += a[j] - a[j + 1];
                    j += 2;
                }
                while (j < 2 * n)
                {
                    t += a[j + 1] - a[j];
                    j += 2;
                }
                s = Math.Max(t, s);
            }
            Console.WriteLine(s);
        }
    }
}