using System;
using System.Linq;

namespace RemoveOddOccurrences
{
    public class RemoveOddOccurrences
    {
        public static void Main()
        {
            var input = Console.ReadLine().Split(new[] { ' ', '\t', '\n' }, StringSplitOptions.RemoveEmptyEntries)
                .Select(int.Parse).ToList();

            input.Sort();
            input.Add(0);

            int currCounter = 1;
            int currNumber = 0;

            for (int i = 1; i < input.Count; i++)
            {
                currNumber = input[i - 1];

                if (input[i] == input[i - 1])
                {
                    currCounter++;
                }
                else
                {
                    if (currCounter %2 == 1)
                    {
                        for (int k = i-currCounter; k <i ; k++)
                        {
                            input[k] = 0;
                        }
                    }
                    currCounter = 1;
                }
            }
            input.RemoveAll(x => x == 0);
            Console.WriteLine(string.Join(" ", input));

        }
    }
}