using System;

public class Program

{

    public static void Main()

    {

        int[] a= new int[] {2,1,5,-6,9};

        Console.WriteLine("Even Count" + solution(a));

    }

    public static int solution(int[] A)

    {

        if (A.Length > 50000)

            return -1;

        for (int Item1 =0; Item1< A.Length; Item1++)

        {

                if (A[Item1] < -1000000000 || A[Item1] > 1000000000  )

                    return -1;

        }

        int EvenCount=0;

        for (int Item1 =0; Item1< A.Length; Item1++)

        {

            for (int Item2  = Item1+1; Item2< A.Length; Item2++)

            {

​

                if( (A[Item1] + A[Item2]) % 2  == 0)

                {

                    EvenCount +=    1;

                }

            }

        }

        if (EvenCount > 1000000000)

            return -1;

        else

            return EvenCount;

    }

}