Phonebook Upgrade

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

namespace _13.PhonebookUpdate
{
    class PhonebookUpdate
    {
        static void Main(string[] args)
        {

            string input = Console.ReadLine();
            SortedDictionary<string, string> phonebook = new SortedDictionary<string, string>();
            List<string> result = new List<string>();
            bool listed = false;

            while (input.ToUpper() != "END")
            {
                if (input == "ListAll")
                {
                    listed = true;
                    input = Console.ReadLine();
                    continue;
                }

                string[] text = input.Split(' ');
                string action = text[0];
                string name = text[1];

                if (action == "A")
                {
                    string number = text[2];
                    if (phonebook.ContainsKey(name))
                        phonebook[name] = number;
                    else
                        phonebook.Add(name, number);
                }
                else if (action == "S")
                {
                    string answer = "";
                    if (phonebook.ContainsKey(name))
                        answer = string.Format("{0} -> {1}", name, phonebook[name]);
                    else
                        answer = string.Format("Contact {0} does not exist.", name);
                    result.Add(answer);
                }
                input = Console.ReadLine();
            }

            if (listed)
            {
                foreach (var contact in phonebook)
                {
                    Console.WriteLine("{0} -> {1}", contact.Key, contact.Value);
                }
            }
            else
            {
                Console.WriteLine(string.Join("\n", result));
            }
        }
    }
}