using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        List<List<int>> matrix= new List<List<int>>(){

                new List<int>(){  1  ,1 , 1  ,1 },  

                new List<int>(){  1  ,0 , 0  ,1 },  

                new List<int>(){  1  ,0 , 0  ,0 },  

                new List<int>(){  1  ,1 , 0  ,1 }

        };

        int result = connectedCell(matrix);

        Console.WriteLine("Connected Cells: " + result);

    }

    public static int getRegionSize(List<List<int>> matrix,int row,int col){

        Console.WriteLine("({0}, {1})",row,col);

        if(row < 0 || col < 0 || row >= matrix.Count || col >= matrix[row].Count)

        {

            return 0;

        }

        if(matrix[row][col] == 0)

        {

            return 0;

        }

        matrix[row][col] = 0;

        int size = 1;

        for(int r= row-1; r <= row+1; r++){

            for(int c = col-1; c <= col +1 ; c++){

             if(r != row || c != col){

                size += getRegionSize(matrix, r, c);       

             }

            }

        }

        return size;

    }

​

    public static int connectedCell(List<List<int>> matrix)

    {

        int maxRegion = 0;

        for(int row=0; row < matrix.Count; row++)

        {

            for (int col = 0 ; col< matrix[row].Count; col++)

            {

                if(matrix[row][col] == 1)

                    {

                        int size = getRegionSize(matrix, row, col);

                        maxRegion = Math.Max(size, maxRegion);

                    }

            }

        }

        return maxRegion;

    }

}