using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(PairWithTargetSum(new int[]{2, 5, 9, 11}, 11));

    }

    public static int[] PairWithTargetSum(int[] arr, int targetSum)

    {

        var result = new int[]{ -1, -1 };

        var p1 = 0;

        var p2 = arr.Length - 1;

        while(p1 < p2)

        {

            var sum = arr[p1] + arr[p2];

            if( sum == targetSum)

            {

                return new int[] {p1, p2};

            }

            if(sum > targetSum)

            {

                p2--;

            }

            else

            {

                p1++;

            }

        }

        return result;

    }

}