Sets & Dictionaries Advanced - 04. Even Times

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

namespace Advanced
{
    class Program
    {
        static void Main(string[] args)
        {
            int number = int.Parse(Console.ReadLine());

            var digits = new Dictionary<int, int>();

            for (int i = 0; i < number; i++)
            {
                int digit = int.Parse(Console.ReadLine());

                if (!digits.ContainsKey(digit))
                {
                    digits[digit] = 0;
                }

                digits[digit]++;

            }
            Console.WriteLine(digits.First(x => x.Value % 2 == 0).Key);
        }
    }
}