Chess Queens

using System;
using System.Collections.Generic;
using System.Linq;

namespace ChessQueens
{
    class ChessQueens
    {
        static void Main()
        {
            int n = int.Parse(Console.ReadLine());
            int distance = int.Parse(Console.ReadLine());
            string[,] board = new string[n, n];
            char initial = 'a';
            List<string> collected = new List<string>();

            for (int i = 0; i < n; i++)
            {
                for (int j = 0; j < n; j++)
                {
                    board[i, j] = Convert.ToString(initial) + Convert.ToString(j + 1);

                }
                initial++;
            }

            if (distance >= n - 1)
            {
                Console.WriteLine("No valid positions");
                return;
            }
            else
            {
                for (int i = 0; i < n; i++)
                {
                    for (int j = 0; j+distance+1 < n; j++)
                    {
                        string[] temp = new string[2] { board[i, j], board[i, j + distance + 1] };
                        string one = temp[0] + " - " + temp[1];
                        string two = temp[1] + " - " + temp[0];
                        collected.Add(one);
                        collected.Add(two);
                    }
                }

                for (int i = 0; i < n; i++)
                {
                    for (int j = 0; j + distance + 1 < n; j++)
                    {
                        string[] temp = new string[2] { board[j, i], board[j + distance + 1, i]};
                        string one = temp[0] + " - " + temp[1];
                        string two = temp[1] + " - " + temp[0];
                        collected.Add(one);
                        collected.Add(two);
                    }
                }
                for (int i = 0; i < n; i++)
                {
                    for (int j = 0; j + distance + 1 < n && i+distance+1 < n; j++)
                    {
                        string[] temp = new string[2] { board[i, j], board[i + distance + 1, j + distance + 1] };
                        string one = temp[0] + " - " + temp[1];
                        string two = temp[1] + " - " + temp[0];
                        collected.Add(one);
                        collected.Add(two);
                    }
                }
                for (int i = 0; i < n; i++)
                {
                    for (int j = n - 1; j - distance - 1 >= 0 && i+distance+1 < n; j--)
                    {
                        string[] temp = new string[2] { board[i, j], board[i+distance+1, j-distance-1] };
                        string one = temp[0] + " - " + temp[1];
                        string two = temp[1] + " - " + temp[0];
                        collected.Add(one);
                        collected.Add(two);
                    }
                }

            }

            List<string> noDupes = collected.Distinct().ToList();

            noDupes.Sort();

            foreach (var item in noDupes)
            {
                Console.WriteLine(item);
            }
        }
    }
}