using System;

public class Program

{

    public static void Main()

    {

        int[,] boldPos = {{4,15}, {35,43}};

        Console.WriteLine(BoldText("The quick brown fox jumps over the lazy dog.",boldPos));

    }

    static string BoldText(string text, int[,] boldPos)

    {

        for(int i = boldPos.GetLength(0)-1; i >=0 ; i--)

        {

            text = InsertBoldBlock(text, new int[2]{boldPos[i,0],boldPos[i,1]});

        }

        return text;

    }

    static string InsertBoldBlock(string text, int[] boldPos)

    {

        string boldBlock = "</b>";

        for(int i = boldPos.Length-1;i >= 0;i--)

        {

            text = text.Insert(boldPos[i],boldBlock); 

            boldBlock = "<b>";

        }

        return text;

    }

}