using System;
using System.Linq;

namespace Largest_Area_in_Matrix
{
    class Program
    {
        static int[,] matrix;
        static bool[,] visited;

        static void Main()
        {
            var sizes = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
            matrix = new int[sizes[0], sizes[1]];
            visited = new bool[sizes[0], sizes[1]];

            for (int row = 0; row < sizes[0]; row++)
            {
                var input = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();

                for (int col = 0; col < sizes[1]; col++)
                {
                    matrix[row, col] = input[col];
                }
            }
            Console.WriteLine(FindMaxArea());
        }

        static int FindMaxArea()
        {
            int maxArea = 0;

            for (int row = 0; row < matrix.GetLength(0); row++)
            {
                for (int col = 0; col < matrix.GetLength(1); col++)
                {
                    maxArea = Math.Max(maxArea, FindMaxArea(row, col, matrix[row, col]));
                }
            }
            return maxArea;
        }

        static int FindMaxArea(int row, int col, int value)
        {
            if (row < 0 || col < 0 || row >= matrix.GetLength(0) || col >= matrix.GetLength(1))
            {
                return 0;
            }
            if (visited[row, col])
            {
                return 0;
            }
            if (matrix[row, col] != value)
            {
                return 0;
            }
            visited[row, col] = true;
            return FindMaxArea(row, col + 1, value) + FindMaxArea(row, col - 1, value) +
            FindMaxArea(row + 1, col, value) + FindMaxArea(row - 1, col, value) + 1;
        }
    }
}