using System;

public class Program

{

    public static void Main()

    {

        //Sample inputs

        long[] input = { 0, 1023, 1024000, 1024000000, 1024000000000L, 1024000000000000L, 1024000000000000000L, long.MaxValue, -1 };

        for (int i = 0; i < input.Length; i++)

        {

            Console.WriteLine(HumanReadableBytes(input[i]));

        }

    }

​

    private static string HumanReadableBytes(long bytes)

    {

        string result = string.Empty;

        int index = 0;

        string[] suffixes = { "Bytes", "KB", "MB", "GB", "TB", "PB", "EB" };

        if (bytes < 0) //input validations

        {

            result = "Not a valid byte size";

        }

        else if (bytes < 1024)

        {

            result = string.Format("{0:n0} {1}", bytes, suffixes[index]);

        }

        else

        {

            decimal temp = bytes;

            while (Math.Round(temp, 1) >= 1000) 

            {

                temp /= 1024;

                index++;

            }

            result = string.Format("{0:n1} {1}", temp, suffixes[index]);

        }

​

        return result;

    }

}