using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

​

namespace n11_17._3._2021

{

    class Program

    {

        static void Main(string[] args)

        {

            List<int> nums = Console.ReadLine().Split().Select(int.Parse).ToList();

            while (nums.Count > 2)

            {

                 for (int i = 1; i < nums.Count - 1; i++)

                 {

                    if (nums[i - 1] == nums[i] && nums[i + 1] == nums[i])

                    {

                          nums.Remove(nums[i]);

                    }

                 }

            }

            if(nums.Count<1)

            {

                Console.WriteLine("Empty");

            }

            Console.WriteLine(string.Join(" ", nums));

        }

    }

}

​