using System;

using System.Collections;

public class Program

{

    public static void Main()

    {

        //Console.WriteLine("Hello World");

​

        // GIVEN AN ARRAY OF INTEGERS, EVERY ELEMENT APPEARS TWICE EXCEPT FOR ONE. FIND THAT ONE.

​

        List<int> input = new List<int>() { 1, 2, 1, 2, 4, 5, 5, 7, 8, 8 };

​

    }

}