using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using System.Diagnostics;
using System.Numerics;
using Enu = System.Linq.Enumerable;

class Program
{
    int H, W;
    string[] grid;
    bool[] seen;
    UnionFind uf;
    Dictionary<int, List<int>> components;
    List<int>[] G;

    public void Solve()
    {
        H = Reader.Int() + 2;
        W = Reader.Int() + 2;
        grid = Surround(Reader.StringArray(H - 2), '.');
        seen = new bool[H * W];
        uf = new UnionFind(H * W);
        memo = new int?[H * W, 2];
        G = new List<int>[H * W];
        for (int i = 0; i < G.Length; i++) G[i] = new List<int>();

        for (int y = 0; y < H; y++)
            for (int x = 0; x < W; x++)
                for (int dy = -1; dy <= 1; dy++)
                    for (int dx = -1; dx <= 1; dx++)
                    {
                        int ny = y + dy, nx = x + dx;
                        if (IsInside(ny, nx) && grid[y][x] == grid[ny][nx] &&
                            (dx == 0 || dy == 0 || grid[y][x] == 'x'))
                            uf.Unite(y * W + x, ny * W + nx);
                    }
        components = uf.Components();
        CheckChild(uf.Root(0));
        int ans = Rec(uf.Root(0), 1, true);
        Console.WriteLine(ans);
    }

    private void CheckChild(int id)
    {
        seen[id] = true;
        var nexts = new HashSet<int>();
        foreach (int cell in components[id])
        {
            int y = cell / W, x = cell % W;
            for (int dy = -1; dy <= 1; dy++)
                for (int dx = -1; dx <= 1; dx++)
                {
                    int ny = y + dy, nx = x + dx;
                    if (!IsInside(ny, nx)) continue;
                    int next = uf.Root(ny * W + nx);
                    if (IsInside(ny, nx) && grid[ny][nx] != grid[y][x] && !seen[next])
                        nexts.Add(next);
                }
        }
        foreach (int next in nexts)
        {
            G[id].Add(next);
            CheckChild(next);
        }
    }

    bool IsInside(int y, int x) { return y >= 0 && y < H && x >= 0 && x < W; }

    int?[,] memo;
    private int Rec(int i, int canUse, bool empty)
    {
        if (memo[i, canUse].HasValue) return memo[i, canUse].Value;
        int res = 0;

        if (empty)
        {
            foreach (int child in G[i])
                res += Rec(child, canUse, !empty);
            return res;
        }

        foreach (int child in G[i])
            res += Rec(child, 1, !empty);
        if (canUse == 1)
        {
            int use = uf.NumElements(i);
            foreach (int child in G[i])
                use += Rec(child, 0, !empty);
            res = Math.Max(res, use);
        }

        memo[i, canUse] = res;
        return res;
    }

    string[] Surround(string[] grid, char c)
    {
        int H = grid.Length + 2, W = grid[0].Length + 2;
        var res = new string[H];
        for (int i = 0; i < H; i++)
            if (i == 0 || i == H - 1) res[i] = new string(c, W);
            else res[i] = c + grid[i - 1] + c;
        return res;
    }

    class UnionFind
    {
        private int[] parent;
        private int[] rank;
        private int[] numElements;

        public UnionFind(int N)
        {
            parent = new int[N];
            rank = new int[N];
            numElements = new int[N];
            for (int i = 0; i < N; i++)
            {
                parent[i] = i;
                numElements[i] = 1;
            }
        }
        public int Root(int x)
        {
            if (parent[x] == x) return x;
            return parent[x] = Root(parent[x]);
        }
        public bool Same(int x, int y)
        {
            return Root(x) == Root(y);
        }
        public int NumElements(int x)
        {
            return numElements[Root(x)];
        }
        public bool Unite(int x, int y)
        {
            x = Root(x); y = Root(y);
            if (x == y) return false;
            if (rank[x] > rank[y]) { var t = x; x = y; y = t; }
            if (rank[x] == rank[y]) rank[y]++;
            parent[x] = y;
            numElements[y] += numElements[x];
            return true;
        }
        public Dictionary<int, List<int>> Components()
        {
            var dic = new Dictionary<int, List<int>>();
            for (int i = 0; i < parent.Length; i++)
            {
                int root = Root(i);
                if (!dic.ContainsKey(root)) dic[root] = new List<int>();
                dic[root].Add(i);
            }
            return dic;
        }
    }
}

class Entry { static void Main() { new Program().Solve(); } }
class Reader
{
    private static TextReader reader = Console.In;
    private static readonly char[] separator = { ' ' };
    private static readonly StringSplitOptions op = StringSplitOptions.RemoveEmptyEntries;
    private static string[] A = new string[0];
    private static int i;
    private static void Init() { A = new string[0]; }
    public static void Set(TextReader r) { reader = r; Init(); }
    public static void Set(string file) { reader = new StreamReader(file); Init(); }
    public static bool HasNext() { return CheckNext(); }
    public static string String() { return Next(); }
    public static int Int() { return int.Parse(Next()); }
    public static long Long() { return long.Parse(Next()); }
    public static double Double() { return double.Parse(Next()); }
    public static int[] IntLine() { return Array.ConvertAll(Split(Line()), int.Parse); }
    public static int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public static int[][] IntTable(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public static string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Next()).ToArray(); }
    public static string Line() { return reader.ReadLine().Trim(); }
    private static string[] Split(string s) { return s.Split(separator, op); }
    private static string Next() { CheckNext(); return A[i++]; }
    private static bool CheckNext()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return CheckNext();
        A = Split(line);
        i = 0;
        return true;
    }
}