Longest Alphabetical Word

using System;
using System.Collections.Generic;
using System.Text;

namespace LongestAlphabeticalWord
{
    class LongestAlphabeticalWord
    {
        static void Main()
        {
            string word = Console.ReadLine();
            int size = int.Parse(Console.ReadLine());
            if (size == 1)
            {
                Console.WriteLine(word[0]);
                return;
            }
            char[,] block = new char[size,size];
            string longest = "";
            char currentLetter = word[0];
            int index = 0;
            List<string> collected = new List<string>();

            for (int i = 0; i < size; i++)
            {
                for (int j = 0; j < size; j++)
                {
                    if (index == word.Length-1)
                    {
                        block[i, j] = currentLetter;
                        index = 0;
                        currentLetter = word[index];
                    }
                    else
                    {
                        block[i, j] = currentLetter;
                        currentLetter = word[index + 1];
                        index++;
                    }
                }
            }
            for (int x = 0; x < 4; x++)
            {
                for (int i = 0; i < size; i++)
                {
                    StringBuilder temp = new StringBuilder();
                    temp.Append(block[i, 0]);
                    char prev = block[i, 0];

                    for (int j = 1; j < size; j++)
                    {
                        if ((int)block[i, j] > (int)prev)
                        {
                            temp.Append(block[i, j]);
                            prev = block[i, j];
                            longest = temp.ToString();
                            collected.Add(temp.ToString());
                        }
                        else
                        {
                            temp.Clear();
                            temp.Append(block[i, j]);
                            prev = block[i, j];
                        }
                    }
                }
                block = RotateMatrix(block, size);
            }
            foreach (var alpha in collected)
            {
                if (alpha.Length>longest.Length)
                {
                    longest = alpha;
                }
            }
            List<string> longestCollection = new List<string>();
            foreach (var alpha in collected)
            {
                if (alpha.Length==longest.Length)
                {
                    longestCollection.Add(alpha);
                }
            }
            foreach (var temp in longestCollection)
            {
                if (string.CompareOrdinal(temp,longest)<0)
                {
                    longest = temp;
                }
            }
            Console.WriteLine(longest);
        }
        static char[,] RotateMatrix(char[,] matrix, int n)
        {
            char[,] ret = new char[n, n];

            for (int i = 0; i < n; ++i)
            {
                for (int j = 0; j < n; ++j)
                {
                    ret[i, j] = matrix[n - j - 1, i];
                }
            }
            return ret;
        }
    }
}