oddNumber

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

namespace Task04
{
    class Task04
    {
        static void Main(string[] args)
        {
            uint n = uint.Parse(Console.ReadLine());
            long[] numbers = new long[n];

            for (uint i = 0; i < n; i++)
            {
                numbers[i] = long.Parse(Console.ReadLine());
            }
            if (n == 1)
            {
                Console.WriteLine(numbers[0]);
            }
            else
            {
                Array.Sort(numbers);
                long temp = numbers[0];
                if (numbers[0] != numbers[1])
                {
                    Console.WriteLine(numbers.Min());
                }
                else if (numbers[0] == numbers[1])
                {
                    for (uint i = 1; i < numbers.Length - 2; i++)
                    {
                        while (numbers[i] == numbers[i + 1] && numbers[i] == numbers[i + 2])
                        {
                            break;
                        }
                        if (i == numbers.Length - 3 && numbers[i + 2] != numbers[i + 1])
                        {
                            Console.WriteLine(numbers[i + 2]);
                break;
                        }

                    }
                }
                else
                {
                    Console.WriteLine(0);
                }
            }
        }
    }
}