using System;

public class Program

{

    public static void Main()

    {

        int[] items = new[] {1,2,3,4,5,6,7,8};

        var index = BinarySearch(items, 3);

        Console.WriteLine("Binary Search index: " + index);

    }

    public static int BinarySearch(int[] items, int item)

    {

        int low = 0;

        int high = items.Length - 1;

        while (low <= high)

        {

            int mid = (low + high) / 2;

            int guess = items[mid];

            if (guess < item) {

                low = mid + 1;

            }

            else if (guess > item) {

                high = mid - 1; 

            }

            else if (guess == item) {

                return mid;

            }

        }

        return -1;

    }

}