Words

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

namespace Words
{
    class Program
    {
        static void Main(string[] args)
        {
            var words = Console.ReadLine()
                .Split(new char[] { ' ', ':', ',', ';', ':', '.', '!', '(', ')', '"',
                '\'', '\\', '/', '[', ']' }, StringSplitOptions.RemoveEmptyEntries)
                .ToList();

            List<string> lowerCaseWords = new List<string>();
            List<string> upperCaseWords = new List<string>();
            List<string> mixedCaseWords = new List<string>();

            foreach (var word in words)
            {
                bool isMixed = false;

                for (int i = 0; i < word.Length; i++)
                {
                    if (!Char.IsLetter(word[i]))
                    {
                        mixedCaseWords.Add(word);
                        isMixed = true;
                        break;
                    }
                }
                if (isMixed == false && word == word.ToUpper())
                {
                    upperCaseWords.Add(word);
                }
                else if (isMixed == false && word == word.ToLower())
                {
                    lowerCaseWords.Add(word);
                }
                else if (isMixed == false)
                {
                    mixedCaseWords.Add(word);
                }
            }

            Console.WriteLine($"Lower-case: {string.Join(", ", lowerCaseWords)}");
            Console.WriteLine($"Mixed-case: {string.Join(", ", mixedCaseWords)}");
            Console.WriteLine($"Upper-case: {string.Join(", ", upperCaseWords)}");

        }
    }
}