02. 2x2 Squares in Matrix from C# Advanced

using System;
using System.Linq;

namespace _2X2_Squares_in_Matrix
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] matrixSizes = Console.ReadLine()
                .Split(" ", StringSplitOptions.RemoveEmptyEntries)
                .Select(int.Parse)
                .ToArray();

            int rows = matrixSizes[0];
            int cols = matrixSizes[1];

            char[,] matrix = ReadMatrix(rows, cols);
            int counter = 0;

            for (int rowIndex = 0; rowIndex < rows - 1; rowIndex++)
            {
                for (int colIndex = 0; colIndex < cols - 1; colIndex++)
                {
                    if (matrix[rowIndex, colIndex] == matrix[rowIndex, colIndex + 1] &&
                        matrix[rowIndex, colIndex] == matrix[rowIndex + 1, colIndex] &&
                        matrix[rowIndex, colIndex] == matrix[rowIndex + 1, colIndex + 1])
                    {
                        counter++;
                    }
                }
            }

            Console.WriteLine(counter);
        }
        static char[,] ReadMatrix(int rows, int cols)
        {
            char[,] matrix = new char[rows, cols];


            for (int rowIndex = 0; rowIndex < rows; rowIndex++)
            {
                char[] inputChars = Console.ReadLine()
                    .Split(' ', StringSplitOptions.RemoveEmptyEntries)
                    .Select(char.Parse)
                    .ToArray();
                for (int colIndex = 0; colIndex < cols; colIndex++)
                {
                    matrix[rowIndex, colIndex] = inputChars[colIndex];
                }
            }

            return matrix;
        }
    }
}