package com.advanced;

import java.io.ByteArrayInputStream;
import java.util.Arrays;
import java.util.Scanner;

public class LargestArea {
    static int rowsIn;
    static int colsIn;
    static int  checkedPosition;

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);
        int[] defineMatrix = Arrays.stream(input.nextLine().split(" ")).mapToInt(Integer::parseInt).toArray();
        rowsIn = defineMatrix[0];
        colsIn = defineMatrix[1];


        int[][] matrix = new int[rowsIn][colsIn];
        for (int row = 0; row < rowsIn; row++) {
            for (int col = 0; col < colsIn; col++) {
                matrix[row][col] = Integer.parseInt(input.next());
            }
        }

        int longestPath = 0;
        int currentValue;
         checkedPosition = 1111;

        for (int rows = 0; rows < rowsIn; rows++) {
            for (int cols = 0; cols < colsIn; cols++) {
                if (matrix[rows][cols] != checkedPosition) {
                    currentValue = matrix[rows][cols];

                    int size = getPathSize(matrix, rows, cols, currentValue);
                    longestPath = Math.max(size, longestPath);
                    matrix[rows][cols] = checkedPosition;
                }
            }
        }
        System.out.println(longestPath);
    }

    private static int getPathSize(int[][] matrix, int rows, int cols, int currentValue) {
        if (!isInRange(matrix, rows, cols)) {
            return 0;
        }
        if (matrix[rows][cols] != currentValue) {
            return 0;
        }

        matrix[rows][cols] = checkedPosition;
        int counter = 1;

        for (int r = rows - 1; r <= rows + 1; r++) {
            for (int c = cols - 1; c <= cols + 1; c++) {
                if (r != rows || c != cols)
                    counter += getPathSize(matrix, r, c, currentValue);
            }
        }
        return counter;
    }

    private static boolean isInRange(int[][] matrix, int rows, int cols) {
        return rows >= 0 && rows < rowsIn && cols >= 0 && cols < colsIn;
    }

}