using System;

using System.Globalization;

​

public class SortedSearch

{

    public static int CountNumbers(int[] sortedArray, int lessThan)

    {

        return CountNumbers(sortedArray, lessThan, 0, sortedArray.Length - 1);

    }

​

    public static int CountNumbers(int[] sortedArray, int lessThan, int startIndex, int endIndex)

    {

        var length = sortedArray.Length;

​

        if (sortedArray == null || length == 0 || sortedArray[startIndex] >= lessThan)

            return startIndex;

        if (sortedArray[endIndex] < lessThan)

            return endIndex + 1;

        var middleIndex = (endIndex + startIndex) / 2;

        var middleValue = sortedArray[middleIndex];

        if (middleValue == lessThan)

            return middleIndex;

        else if (middleValue > lessThan)

            return CountNumbers(sortedArray, lessThan, startIndex, middleIndex - 1);

        else

            return CountNumbers(sortedArray, lessThan, middleIndex + 1, endIndex);

​

    }

    public static void Main(string[] args)

    {

        Console.WriteLine(SortedSearch.CountNumbers(new int[] { 1, 3, 5, 7 }, 4));

    }

}