7.00 To Uppercase

using System;
using System.IO;
using System.Text.RegularExpressions;

class ToUppercase
{
    static void Main()
    {
        int bufSize = 32766;
        Stream inStream = Console.OpenStandardInput(bufSize);
        Console.SetIn(new StreamReader(inStream, Console.InputEncoding, false, bufSize));

        string text = Console.ReadLine();

        string startUpcase = "<upcase>";
        string endUpcase = "</upcase>";
        int countStarUpcase = Regex.Matches(Regex.Escape(text), startUpcase).Count;
        int countEndcase = Regex.Matches(Regex.Escape(text), endUpcase).Count;
        string result = string.Empty;

        if (countStarUpcase >= 1)
        {
            for (int i = 0; i < Math.Min(countStarUpcase, countEndcase); i++)
            {
                int startIndex = text.IndexOf(startUpcase);
                int endIndex = text.IndexOf(endUpcase);

                string replaceText = text.Substring(startIndex + startUpcase.Length,
                    endIndex - startIndex - endUpcase.Length + 1);
                string modifiers = replaceText.ToUpper();
                result = text.Replace(replaceText, modifiers);
                result = result.Remove(startIndex, startUpcase.Length);
                result = result.Remove(startIndex + modifiers.Length, endUpcase.Length);
                text = result;
            }
            Console.WriteLine(result);
        }
        else
        {
            Console.WriteLine(text);
        }
    }
}