using System;

using System.Collections.Generic;

public class Program

{

    public static int run = 0;

    public static void Main()

    {

        List<int> numbers = new List<int>() { 1, 5, 7, 9, 12, 13, 14, 16, 18, 19, 21 };

        //int askingNumber = int.Parse(Console.ReadLine());

        bool numberIsFound = DivideAndConquer(numbers, 19);

        Console.WriteLine(numberIsFound);

​

    }

    public static bool DivideAndConquer(List<int> numbers, int askingNumber){

        run++;

        int middleIndex = (numbers.Count - 1) / 2;

        int indexes = numbers.Count - 1;

        Console.WriteLine("Indexes : " + indexes);

        Console.WriteLine("Middle Index : " + middleIndex);

        //Console.WriteLine("Middle Number : " + numbers[middleIndex]);

        Console.WriteLine(run + " ------------------------------------------- " + numbers[0]);

​

        if(numbers.Count == 1 )

        {

            if(numbers[0] != askingNumber)

                return false;

            else

                return true;

        }

        if(numbers[middleIndex] == askingNumber)

        {

            Console.WriteLine("True");

            return true;

        }

        if(askingNumber > numbers[middleIndex])

            return DivideAndConquer(numbers.GetRange(middleIndex + 1, indexes - middleIndex), askingNumber);

        if(askingNumber < numbers[middleIndex])

            return DivideAndConquer(numbers.GetRange(0, middleIndex), askingNumber);

        return false;

    }

}