Exam 3. Magic Strings

namespace _4.MagicStrings
{
    using System;

    public class MagicStrings
    {
        public static void Main(string[] args)
        {
            checked
            {
                int diff = int.Parse(Console.ReadLine());

                char[] letters = { 'k', 'n', 'p', 's' };
                bool foundMagicString = false;
                foreach (char a in letters)
                {
                    foreach (char b in letters)
                    {
                        foreach (char c in letters)
                        {
                            foreach (char d in letters)
                            {
                                int firstWeight = CalculateWeightOfFourLetters(a, b, c, d);
                                foreach (char e in letters)
                                {
                                    foreach (char f in letters)
                                    {
                                        foreach (char g in letters)
                                        {
                                            foreach (char h in letters)
                                            {
                                                int secondWeight = CalculateWeightOfFourLetters(e, f, g, h);
                                                int currentDiff = Math.Abs(firstWeight - secondWeight);
                                                if (currentDiff == diff)
                                                {
                                                    foundMagicString = true;
                                                    Console.WriteLine("{0}{1}{2}{3}{4}{5}{6}{7}", a, b, c, d, e, f, g, h);
                                                }
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }

                if (!foundMagicString)
                {
                    Console.WriteLine("No");
                }
            }
        }

        private static int CalculateWeightOfFourLetters(char letter1, char letter2, char letter3, char letter4)
        {
            checked
            {
                int sumWeight = 0;
                sumWeight += CalculateWeightOfEachLetter(letter1);
                sumWeight += CalculateWeightOfEachLetter(letter2);
                sumWeight += CalculateWeightOfEachLetter(letter3);
                sumWeight += CalculateWeightOfEachLetter(letter4);
                return sumWeight;
            }
        }

        private static int CalculateWeightOfEachLetter(char letter)
        {
            checked
            {
                switch (letter)
                {
                    case 'k':
                        return 1;
                    case 'n':
                        return 4;
                    case 'p':
                        return 5;
                    case 's':
                        return 3;
                    default:
                        return 0;
                }
            }
        }
    }
}