using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Digite un mensaje:");

        var message = Console.ReadLine();

        Console.WriteLine("Digite un caracter para buscar dentro del mensaje:");

        var caracter = Console.ReadLine();

        Console.WriteLine("Digite un caracter para reemplazar por el caracter encontrado:");

        var reemplazo = Console.ReadLine();     

        //take a message to become to word

        string[] words = message.Split(' ');

        foreach (var word in words)

        {

            //Console.WriteLine(word);

            var message_with_replacements = search_rescue(word, caracter, reemplazo);

            Console.WriteLine(message_with_replacements);//to show a new message

        }

    }

    public static string search_rescue (string message, string character_searched, string replacement) {

        var last_index = message.LastIndexOf(character_searched);

        //take a word to became to charArray

        char[] letters = message.ToCharArray();

        var message_final = "";

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

        {

          //Console.WriteLine(letters[i]);

            var temp = letters[i].ToString();

            if(i != 0 && i != letters.Length-1 && 

               temp == character_searched && 

               letters.Length+replacement.Length < 10 &&

               last_index == i) {//completed contidion a and b

                var coince_replace = temp.Replace(character_searched, replacement);

                temp = coince_replace;

            }

            message_final =  message_final + temp;

            //Console.WriteLine(letters);

        }

        return message_final;

    }

}