백준 C# - 7785

코드 전문

using System;
using System.Collections.Generic;
using System.Text;
namespace baek2
{
    class Program
    {
        public static void Main()
        {
            int n = int.Parse(Console.ReadLine());
            Dictionary<string, string> ht = new Dictionary<string, string>();
            StringBuilder sb = new StringBuilder();
            for(int i = 0; i< n;i++)
            {
                string[] token = Console.ReadLine().Split();
                if(ht.ContainsKey(token[0])) ht.Remove(token[0]);
                else ht.Add(token[0], token[1]);
            }
            var keys = new List<string>(ht.Keys);

            keys.Sort();
            keys.Reverse();
            foreach (var key in keys)
            {
                sb.AppendLine(key.ToString());
            }
            Console.WriteLine(sb.ToString());
        }
    }
}