using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] rules = new[] { "a->c", "dd->.c" };

            string inpitString = "dda";
            bool ruleApplied = false;
            bool lastRule = false;

            do
            {
                ruleApplied = false;
                for (int i = 0; i < rules.Length; i++)
                {
                    string[] ruleParts = rules[i].Split(new[] { "->.", "->" }, StringSplitOptions.None);

                    if (inpitString.Contains(ruleParts[0]))
                    {
                        if (ruleParts[0] == "Ë")
                            inpitString = ruleParts[1] + inpitString;
                        else
                        {
                            Regex search = new Regex(ruleParts[0]);
                            inpitString = search.Replace(inpitString, ruleParts[1], 1, 0);
                        }
                        ruleApplied = true;
                        if (rules[i].Contains("->."))
                            lastRule = true;
                        break;
                    }
                }
            }
            while (ruleApplied && !lastRule);
        }
    }
}