using System;

​

public class OddNumber

{

    public static void Main()

    {

        int n = int.Parse(Console.ReadLine());

        long[] numbers = new long[n];

        for (int i = 0; i < n; i++)

        {

            numbers[i] = long.Parse(Console.ReadLine());

        }

​

        Array.Sort(numbers);

        int counter = 1;

        long oddNumber = 0;

        if (n == 1)

        {

            Console.WriteLine(numbers[n - 1]);

            return;

        }

​

        if (numbers[n - 1] != numbers[n-2])

        {

            Console.WriteLine(numbers[n - 1]);

            return;

        }

        for (int i = 0; i < numbers.Length - 1; i++)

        {

            if (numbers[i] == numbers[i+1])

            {

                counter++;

            }

            else

            {

                if (counter % 2 != 0)

                {

                    Console.WriteLine(numbers[i]);

                    return;

                }

                else

                {

                    counter = 1;

                }

            }

        }

        if (counter % 2 != 0)

        {

            oddNumber = numbers[n - 1];

        }

        Console.WriteLine(oddNumber);

    }

}

​

​