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

namespace Algorithm
{
    class Program
    {
        static void Main(string[] args)
        {
            var n = int.Parse(Console.ReadLine());
            var a = Console.ReadLine().Split().Select(int.Parse).ToArray();

            var continuous = new List<int>();
            var cur = a[0];
            var count = 1;
            for (var i = 1; i < n; i++)
            {
                if (cur == a[i])
                    count++;
                else
                {
                    continuous.Add(count);
                    count = 1;
                }

                cur = a[i];
            }
            continuous.Add(count);

            var total = 0;
            for (var i = 0; i < continuous.Count; i++)
            {
                if (i % 2 == 0) total += continuous[i];
                else
                {
                    if (i == continuous.Count - 1)
                        total += Math.Max(continuous[i] - 1, 0);
                    else
                        total += Math.Max(continuous[i] - 2, 0);
                }
            }

            var total2 = 0;
;            for (var i = 0; i < continuous.Count; i++)
            {
                if (i % 2 == 1) total2 += continuous[i];
                else
                {
                    if (i == 0)
                        total2 += Math.Max(continuous[i] - 1, 0);
                    else
                        total2 += Math.Max(continuous[i] - 2, 0);
                }
            }

            Console.WriteLine(Math.Max(total, total2));
        }
    }
}