using System;
using System.Text;
using System.Collections.Generic;

namespace Assignment
{
	public struct BoldText
	{
        public int indexFirst;
        public int indexLast;
    }

    public class Program
    {
        public static void Main(string[] args)
        {
            List<BoldText> bold = new List<BoldText>();

			Console.WriteLine("Type the text You want to change");
			string text = Console.ReadLine();

			int inputEnd = 1;

			while(inputEnd != 0)
			{
				Console.WriteLine("Declare the beginning of the bolded text");
				int first = Convert.ToInt32(Console.ReadLine());

				Console.WriteLine("Declare the ending of the bolded text");
				int last = Convert.ToInt32(Console.ReadLine());

				bold.Add( new BoldText {indexFirst = first, indexLast = last} );

				Console.WriteLine("If You want to stop declaring, type 0, otherwise type any other number");
				inputEnd = Convert.ToInt32(Console.ReadLine());
			}
            changeToHtml(text, bold);
        }

        public static void changeToHtml(string text, List<BoldText> bold)
        {
            int textLength = text.Length;
			bool[] isCharTagged = new bool[textLength];

            foreach(BoldText bText in bold)
            {
                if((bText.indexFirst < textLength) && (bText.indexFirst+bText.indexLast < textLength))	// Verification if indexes do not exceed the length.
                {
                    var changedText = new StringBuilder();							// A new string, where the new text will be written.
                    int letter = 0;													// Sort of a index of the text (excluding the HTML tag).
                    char prev = ' ';												// A variable for the "previous" character.

                    foreach (char curr in text)
                    {
						if((letter == 0) && (letter == bText.indexFirst))
						{
							changedText.Append("<b>");								// The HTML tag for the begging of the bold text is added.

							if (letter == (bText.indexFirst+bText.indexLast))
							{
								changedText.Append("</b>");							// The HTML tag for the ending of the bold text is added.
							}
						}

                        changedText.Append(curr);									// Adding the character to the string.

                        if((!isTag(prev, curr))  && (!isCharTagged[bText.indexFirst]) && (!isCharTagged[bText.indexFirst+bText.indexLast]))
                        {
                            if (++letter == bText.indexFirst)						// If the number of the letter equals the first index.
                            {
                                changedText.Append("<b>");								// The HTML tag for the begging of the bold text is added.
                            }
                            if (letter == (bText.indexFirst+bText.indexLast))		// If the number of the letter equals the last index.
                            {
                                changedText.Append("</b>");                              // The HTML tag for the ending of the bold text is added.
                            }
                        }
                        prev = curr;												// Saving the character (it becomes the "previous" one).
                    }

                    for (int j = bText.indexFirst; j < (bText.indexFirst+bText.indexLast); j++) 		// The text between the indexes is tagged.
					{
                        isCharTagged[j] = true;
                    }

                    text = changedText.ToString();
                }
            }
            Console.WriteLine(text);
        }

        public static bool isTag(char prev, char curr)
		{
            if ((curr == '<') || (curr == '/') || ((curr == 'b') && ((prev == '<') || (prev == '/'))) || (curr == '>'))
                return true;
            else
                return false;
        }
    }
}