using System;

using System.Collections.Generic;

public class Program

{

    private static int MaxIsland(int[,] ocean) {

        int result = 0;

​

        if (ocean == null)

            return result;

​

        var visited = new HashSet<(int y, int x)>();

​

        for (int y = 0; y < ocean.GetLength(0); ++y)

             for (int x = 0; x < ocean.GetLength(1); ++x) {

                 if (ocean[y, x] != 0)

                     continue;

                 if (!visited.Add((y, x)))

                     continue;

​

                 int current = 1;

                 var agenda = new Queue<(int y, int x)>();

​

                 agenda.Enqueue((y, x));

​

                 while (agenda.Count > 0) {

                     var (r, c) = agenda.Dequeue();

                     for (int d = 0; d < 4; ++d) {

                         int newR = r + (d - 1) % 2;

                         int newC = c + (d - 2) % 2;

​

                         if (newC < 0 || newR < 0 || newR >= ocean.GetLength(0) || newC >= ocean.GetLength(1))

                             continue;

                         if (ocean[newR, newC] != 0)

                             continue;

                         if (visited.Add((newR, newC))) {

                             agenda.Enqueue((newR, newC));

                             current += 1;

                         }

                     }

                 }

​

                 result = Math.Max(result, current);

             }

​

        return result;

    }

    public static void Main()

    {

        int[,] ocean = {

            { 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, },

            { 1, 0, 1, 0, 0, 0, 0, 1, 1, 1, },

            { 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, },

            { 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, },

            { 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, },

            { 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, },

            { 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, },

        };

​

        int result = MaxIsland(ocean);

        Console.Write(result);

    }

}