3x3 Platform Max Sum (Exercise)

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

namespace ConsoleTesting3
{
    class ConsoleTesting3
    {
        static void Main()
        {
            int n = int.Parse(Console.ReadLine());
            int m = int.Parse(Console.ReadLine());
            var board = new int[n, m];
            var sums = new List<int>();
            var platforms = new List<int[,]>();

            for (int i = 0; i < n; i++)
            {
                for (int j = 0; j < m; j++)
                {
                    Console.Write("Index {0},{1}: ", i,j);
                    board[i, j] = int.Parse(Console.ReadLine());
                }
            }

            Console.WriteLine(new string('=',30));

            for (int i = 0; i < n && i+2 < n; i++)
            {
                for (int j = 0; j < m && j+2 < m; j++)
                {
                    int[,] temp = new int[3,3]
                    {
                        {board[i,j], board[i,j+1], board[i,j+2]} ,
                        {board[i+1,j], board[i+1,j+1], board[i+1,j+2]},
                        {board[i+2,j], board[i+2,j+1], board[i+2,j+2]}
                    };

                    platforms.Add(temp);
                    int sum = 0;

                    foreach (var value in temp)
                    {
                        sum += value;
                    }

                    sums.Add(sum);

                }
            }

            for (int i = 0; i < n; i++)
            {
                for (int j = 0; j < m; j++)
                {
                    string temp = string.Join("", board[i, j]);
                    Console.Write(temp.PadRight(4,' '));
                }
                Console.WriteLine();
            }
            Console.WriteLine(new string('=',30));
            var maxIndex = sums.IndexOf(sums.Max());

            Console.WriteLine("Platform 3x3 with maximal sum({0}):",sums.Max());

            for (int i = 0; i < 3; i++)
            {
                for (int j = 0; j < 3; j++)
                {
                    string temp = string.Join("", platforms[maxIndex][i, j]);
                    Console.Write(temp.PadRight(4,' '));
                }
                Console.WriteLine();
            }
            Console.WriteLine();

        }
    }
}