using System;

namespace Example77
{
	/// <summary>
	/// Summary description for Class1.
	/// </summary>
	class Class1
	{
		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main(string[] args)
		{
			int[] data = { 2, 5, 7, 12, 23, 34, 56, 78, 99, 123, 234, 345, 567 };

			Console.Write("Enter the search key: ");
			int key = int.Parse(Console.ReadLine());

			int index = Search(data, key, 0, data.Length - 1);

			if (index == -1)
				Console.WriteLine("Key {0} was not found", key);
			else
				Console.WriteLine("Key {0} was found at index {1}",
					key, index);
		}

		static int Search(int[] data, int key, int left, int right)
		{
			if (left <= right)
			{
				int middle = (left + right) / 2;

				if (data[middle] == key)
					return middle;
				else
					if (key < data[middle])
						Search(data, key, left, middle - 1);
				else
					Search(data, key, middle + 1, right);
			}

			return -1;
		}
	}
}