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

namespace SoloLearn
{


    class Program
    {

        public static int find_it(int[] seq)
        {

            int count = 0;

            for (int k = 0; k < seq.Length; k++)
            {
                for (int i = k; i < seq.Length - 1; i++)
                {
                    if (seq[k] == seq[i])
                    {
                        count++;

                    }
                }
            }
            if (count % 2 == 0)

            return count;
        }


        static void Main(string[] args)
        {
            int[] oddArr = { 20, 1, -1, 2, -2, 3, 3, 5, 5, 1, 2, 4, 20, 4, -1, -2, 5 };
            Console.WriteLine(find_it(oddArr));


        }
    }
}