Maximal Sum

/* Write a program that reads a rectangular integer matrix of size N x M and finds in it the square 3 x 3 that has maximal sum of its elements.
 * On the first line, you will receive the rows N and columns M. On the next N lines you will receive each row with its columns.
 * Print the elements of the 3 x 3 square as a matrix, along with their sum. */

namespace _02.MaximalSum
{
    using System;
    using System.Linq;

    class MaximalSum
    {
        private static int[,] _matrix;

        static void Main(string[] args)
        {
            Console.WriteLine("Enter two Positive Integer numbers on single line each, separated by a space, for sizes of your matrix: ");
            int[] sizes = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();

            if (sizes.Length < 2 || sizes[0] < 3 || sizes[1] < 3)
            {
                Console.WriteLine("Error!!! - Invalid matrix sizes!");
                return;
            }

            _matrix = new int[sizes[0], sizes[1]];
            Console.WriteLine("Enter your matrix content, each row on single line, each number, separated by a space: ");
            for (int row = 0; row < _matrix.GetLength(0); row++)
            {
                string[] numStr = Console.ReadLine().Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
                if (numStr.Length != _matrix.GetLength(1))
                {
                    Console.WriteLine("Error!!! - Invalid input!");
                    return;
                }

                for (int col = 0; col < _matrix.GetLength(1); col++)
                {
                    _matrix[row, col] = int.Parse(numStr[col]);
                }
            }

            int[] maxSumSquare = FindMaximalSumSquare3x3InMatrix();
            PrintResults(maxSumSquare);
        }

        private static int[] FindMaximalSumSquare3x3InMatrix()
        {
            int[] maxSums = new[] { int.MinValue, 0, 0 };
            for (int row = 0; row + 2 < _matrix.GetLength(0); row++)
            {
                for (int col = 0; col + 2 < _matrix.GetLength(1); col++)
                {
                    int sum = _matrix[row, col] + _matrix[row, col + 1] + _matrix[row, col + 2] + _matrix[row + 1, col] + _matrix[row + 1, col + 1] + _matrix[row + 1, col + 2] + _matrix[row + 2, col] + _matrix[row + 2, col + 1] + _matrix[row + 2, col + 2];
                    if (maxSums[0] < sum)
                    {
                        maxSums[0] = sum;
                        maxSums[1] = row;
                        maxSums[2] = col;
                    }
                }
            }

            return maxSums;
        }

        private static void PrintResults(int[] results)
        {
            Console.WriteLine();
            Console.WriteLine("Sum = {0}", results[0]);
            Console.WriteLine();
            for (int row = results[1]; row < results[1] + 3; row++)
            {
                for (int col = results[2]; col < results[2] + 3; col++)
                {
                    Console.Write("{0,3} ", _matrix[row, col]);
                }
                Console.WriteLine();
            }
            Console.WriteLine();
        }
    }
}