using System;

public class Program

{

    public void Main()

    {

        var arr = new int[]{0,1,3,3,4,5,7,6,8,9};

        Array.Sort(arr);

        for(var i =0; i < arr.Length;i++)

            Console.Write(string.Format("{0}, ", arr[i]));

        var result = recFunc(arr, 6, 0, arr.Length-1);

        Console.WriteLine(result);

    }

    int recFunc(int[] arr, int num, int start, int end)

    {       

        if(num == arr[start])

            return start;

        else

            if(num == arr[end])

                return end;

            else

                if(end - start > 1)

                {

                    if(num < arr[end/2] && num > arr[start])

                        return recFunc(arr, num, start, (end/2));

                    else

                        return recFunc(arr, num, end/2, end);

                }

                else

                    return -1;  

    }

}